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MYSQLD(8)		     MySQL Database System		     MYSQLD(8)

NAME
       mysqld - the MySQL server

SYNOPSIS
       mysqld [options]

DESCRIPTION
       mysqld is the MySQL server. The following discussion covers these MySQL
       server configuration topics:

       ·  Startup options that the server supports

       ·  Server system variables

       ·  Server status variables

       ·  How to set the server SQL mode

       ·  The server shutdown process

Note: Not all storage engines (also known in older versions of MySQL as “table
types”) are supported by all MySQL server binaries and configurations. To find
out how to determine which storage engines are supported by your MySQL server
installation, see Section 5.4.8, “SHOW ENGINES Syntax”.

COMMAND OPTIONS
       When you start the mysqld server, you can specify program options using
       any of the methods described in Section 3, “Specifying Program
       Options”. The most common methods are to provide options in an option
       file or on the command line. However, in most cases it is desirable to
       make sure that the server uses the same options each time it runs. The
       best way to ensure this is to list them in an option file. See
       Section 3.2, “Using Option Files”.

       mysqld reads options from the [mysqld] and [server] groups.
       mysqld_safe reads options from the [mysqld], [server], [mysqld_safe],
       and [safe_mysqld] groups.  mysql.server reads options from the [mysqld]
       and [mysql.server] groups.

       An embedded MySQL server usually reads options from the [server],
       [embedded], and [xxxxx_SERVER] groups, where xxxxx is the name of the
       application into which the server is embedded.

       mysqld accepts many command options. For a list, execute mysqld --help.
       Before MySQL 4.1.1, --help prints the full help message. As of 4.1.1,
       it prints a brief message; to see the full list, use mysqld --verbose
       --help.

       The following list shows some of the most common server options.
       Additional options are described in other sections:

       ·  Options that affect security: See Section 5.3, “Security-Related
	  mysqld Options”.

       ·  SSL-related options: See Section 7.7.3, “SSL Command Options”.

       ·  Binary log control options: See Section 10.4, “The Binary Log”.

       ·  Replication-related options: See Section 8, “Replication Startup
	  Options”.

       ·  Options specific to particular storage engines: See Section 1.1,
	  “MyISAM Startup Options”, Section 5.3, “BDB Startup Options”,
	  Section 2.5, “InnoDB Startup Options and System Variables”, and
	  Section 6.5.1, “MySQL Cluster-Related Command Options for mysqld”.

You can also set the values of server system variables by using variable names
as options, as described later in this section.

·  --help, -?

   Display a short help message and exit. Before MySQL 4.1.1, --help displays
   the full help message. As of 4.1.1, it displays an abbreviated message
   only. Use both the --verbose and --help options to see the full message.

·  --allow-suspicious-udfs

   This option controls whether user-defined functions that have only an xxx
   symbol for the main function can be loaded. By default, the option is off
   and only UDFs that have at least one auxiliary symbol can be loaded; this
   prevents attempts at loading functions from shared object files other than
   those containing legitimate UDFs. This option was added in MySQL 4.0.24,
   and 4.1.10a. See Section 2.4.6, “User-Defined Function Security
   Precautions”.

·  --ansi

   Use standard (ANSI) SQL syntax instead of MySQL syntax. For more precise
   control over the server SQL mode, use the --sql-mode option instead. See
   Section 9.3, “Running MySQL in ANSI Mode”, and the section called “SQL
   MODES”.

·  --basedir=path, -b path

   The path to the MySQL installation directory. All paths are usually
   resolved relative to this directory.

·  --big-tables

   Allow large result sets by saving all temporary sets in files. This option
   prevents most “table full” errors, but also slows down queries for which
   in-memory tables would suffice. Since MySQL 3.23.2, the server is able to
   handle large result sets automatically by using memory for small temporary
   tables and switching to disk tables where necessary.

·  --bind-address=IP

   The IP address to bind to.

·  --bootstrap

   This option is used by the mysql_install_db script to create the MySQL
   privilege tables without having to start a full MySQL server.

·  --character-sets-dir=path

   The directory where character sets are installed. See Section 9.1, “The
   Character Set Used for Data and Sorting”.

·  --character-set-client-handshake

   Don't ignore character set information sent by the client. To ignore client
   information and use the default server character set, use
   --skip-character-set-client-handshake; this makes MySQL 4.1 and higher
   behave like MySQL 4.0. This option was added in MySQL 4.1.15.

·  --character-set-server=charset_name, -C charset_name

   Use charset_name as the default server character set. See Section 9.1, “The
   Character Set Used for Data and Sorting”. If you use this option to specify
   a non-default character set, you should also use --collation-server to
   specify the collation. This option is available as of MySQL 4.1.3.

·  --chroot=path

   Put the mysqld server in a closed environment during startup by using the
   chroot() system call. This is a recommended security measure as of MySQL
   4.0. (MySQL 3.23 is not able to provide a chroot() jail that is 100%
   closed.) Note that use of this option somewhat limits LOAD DATA INFILE and
   SELECT ... INTO OUTFILE.

·  --collation-server=collation_name

   Use collation_name as the default server collation. This option is
   available as of MySQL 4.1.3. See Section 9.1, “The Character Set Used for
   Data and Sorting”.

·  --console

   (Windows only.) Write error log messages to stderr and stdout even if
   --log-error is specified.  mysqld does not close the console window if this
   option is used.

·  --core-file

   Write a core file if mysqld dies. For some systems, you must also specify
   the --core-file-size option to mysqld_safe. See mysqld_safe(1). Note that
   on some systems, such as Solaris, you do not get a core file if you are
   also using the --user option.

·  --datadir=path, -h path

   The path to the data directory.

·  --debug[=debug_options], -# [debug_options]

   If MySQL is configured with --with-debug, you can use this option to get a
   trace file of what mysqld is doing. The debug_options string often is
   ´d:t:o,file_name'. The default is ´d:t:i:o,mysqld.trace'. See Section 1.2,
   “Creating Trace Files”.

·  --default-character-set=charset_name, -C charset_name

   Use charset_name as the default character set. This option is deprecated in
   favor of --character-set-server as of MySQL 4.1.3. See Section 9.1, “The
   Character Set Used for Data and Sorting”.

·  --default-collation=collation_name

   Use collation_name as the default collation. This option is deprecated in
   favor of --collation-server as of MySQL 4.1.3. See Section 9.1, “The
   Character Set Used for Data and Sorting”.

·  --default-storage-engine=type

   This option is a synonym for --default-table-type. It is available as of
   MySQL 4.1.2.

·  --default-table-type=type

   Set the default table type (storage engine) for tables. See Chapter 14,
   Storage Engines and Table Types.

·  --default-time-zone=timezone

   Set the default server time zone. This option sets the global time_zone
   system variable. If this option is not given, the default time zone is the
   same as the system time zone (given by the value of the system_time_zone
   system variable. This option is available as of MySQL 4.1.3.

·  --delay-key-write[={OFF|ON|ALL}]

   Specify how to use delayed key writes. Delayed key writing causes key
   buffers not to be flushed between writes for MyISAM tables.	OFF disables
   delayed key writes.	ON enables delayed key writes for those tables that
   were created with the DELAY_KEY_WRITE option.  ALL delays key writes for
   all MyISAM tables. Available as of MySQL 4.0.3. See Section 5.2, “Tuning
   Server Parameters”, and Section 1.1, “MyISAM Startup Options”.

   Note: If you set this variable to ALL, you should not use MyISAM tables
   from within another program (such as another MySQL server or myisamchk)
   when the tables are in use. Doing so leads to index corruption.

·  --delay-key-write-for-all-tables

   Old form of --delay-key-write=ALL for use prior to MySQL 4.0.3. As of
   4.0.3, use --delay-key-write instead.

·  --des-key-file=file_name

   Read the default DES keys from this file. These keys are used by the
   DES_ENCRYPT() and DES_DECRYPT() functions.

·  --enable-named-pipe

   Enable support for named pipes. This option applies only on Windows NT,
   2000, XP, and 2003 systems, and can be used only with the mysqld-nt and
   mysqld-max-nt servers that support named-pipe connections.

·  --exit-info[=flags], -T [flags]

   This is a bit mask of different flags that you can use for debugging the
   mysqld server. Do not use this option unless you know exactly what it does!

·  --external-locking

   Enable external locking (system locking), which is disabled by default as
   of MySQL 4.0. Note that if you use this option on a system on which lockd
   does not fully work (such as Linux), it is easy for mysqld to deadlock.
   This option was named --enable-locking before MySQL 4.0.3.

   Note: If you use this option to enable updates to MyISAM tables from many
   MySQL processes, you must ensure that the following conditions are
   satisfied:

   ·  You should not use the query cache for queries that use tables that are
      updated by another process.

   ·  You should not use --delay-key-write=ALL or DELAY_KEY_WRITE=1 on any
      shared tables.

   The easiest way to ensure this is to always use --external-locking together
   with --delay-key-write=OFF and --query-cache-size=0. (This is not done by
   default because in many setups it is useful to have a mixture of the
   preceding options.)

·  --flush

   Flush (synchronize) all changes to disk after each SQL statement. Normally,
   MySQL does a write of all changes to disk only after each SQL statement and
   lets the operating system handle the synchronizing to disk. See
   Section 4.2, “What to Do If MySQL Keeps Crashing”.

·  --init-file=file_name

   Read SQL statements from this file at startup. Each statement must be on a
   single line and should not include comments.

·  --innodb-safe-binlog

   Adds consistency guarantees between the content of InnoDB tables and the
   binary log. See Section 10.4, “The Binary Log”.

·  --innodb-xxx

   The InnoDB options are listed in Section 2.5, “InnoDB Startup Options and
   System Variables”.

·  --language=lang_name, -L lang_name

   Return client error messages in the given language.	lang_name can be given
   as the language name or as the full pathname to the directory where the
   language files are installed. See Section 9.2, “Setting the Error Message
   Language”.

·  --log[=file_name], -l [file_name]

   Log connections and SQL statements received from clients to this file. See
   Section 10.2, “The General Query Log”. If you omit the filename, MySQL uses
   host_name.log as the filename.

·  --log-bin[=base_name]

   Enable binary logging. The server logs all statements that change data to
   the binary log, which is used for backup and replication. See Section 10.4,
   “The Binary Log”.

   The option value, if given, is the basename for the log sequence. The
   server creates binary log files in sequence by adding a numeric suffix to
   the basename. It is recommended that you specify a basename (see
   Section 8.4, “Open Issues in MySQL”, for the reason). Otherwise, MySQL uses
   host_name-bin as the basename.

·  --log-bin-index[=file_name]

   The index file for binary log filenames. See Section 10.4, “The Binary
   Log”. If you omit the filename, and if you didn't specify one with
   --log-bin, MySQL uses host_name-bin.index as the filename.

·  --log-error[=file_name]

   Log errors and startup messages to this file. See Section 10.1, “The Error
   Log”. If you omit the filename, MySQL uses host_name.err. If the filename
   has no extension, the server adds an extension of .err.

·  --log-isam[=file_name]

   Log all ISAM/MyISAM changes to this file (used only when debugging
   ISAM/MyISAM).

·  --log-long-format

   Log extra information to the update log, binary update log, and slow query
   log, if they have been activated. For example, the username and timestamp
   are logged for queries. Before MySQL 4.1, if you are using
   --log-slow-queries and --log-long-format, queries that are not using
   indexes also are logged to the slow query log.  --log-long-format is
   deprecated as of MySQL version 4.1, when --log-short-format was introduced.
   (Long log format is the default setting since version 4.1.) Also note that
   starting with MySQL 4.1, the --log-queries-not-using-indexes option is
   available for the purpose of logging queries that do not use indexes to the
   slow query log.

·  --log-queries-not-using-indexes

   If you are using this option with --log-slow-queries, queries that do not
   use indexes also are logged to the slow query log. This option is available
   as of MySQL 4.1. See Section 10.5, “The Slow Query Log”.

·  --log-short-format

   Log less information to the update log, binary update log, and slow query
   log, if they have been activated. For example, the username and timestamp
   are not logged for queries. This option was introduced in MySQL 4.1.

·  --log-slow-admin-statements

   Log slow administrative statements such as OPTIMIZE TABLE, ANALYZE TABLE,
   and ALTER TABLE to the slow query log.

   This option was added in MySQL 4.1.13. (It is unnecessary in MySQL 4.0
   because slow administrative statements are logged by default.)

·  --log-slow-queries[=file_name]

   Log all queries that have taken more than long_query_time seconds to
   execute to this file. See Section 10.5, “The Slow Query Log”. Note that the
   default for the amount of information logged has changed in MySQL 4.1. See
   the --log-long-format and --log-short-format options for details.

·  --log-update[=file_name]

   Log updates to fileN where N is a unique number if not given. See
   Section 10.3, “The Update Log”. The update log is now deprecated; you
   should use the binary log instead (--log-bin). See Section 10.4, “The
   Binary Log”.

·  --log-warnings[=level], -W [level]

   Print out warnings such as Aborted connection...  to the error log.
   Enabling this option is recommended, for example, if you use replication
   (you get more information about what is happening, such as messages about
   network failures and reconnections). This option is enabled by default as
   of MySQL 4.0.19 and 4.1.2; to disable it, use --log-warnings=0. As of MySQL
   4.0.21 and 4.1.3, a level argument can be given. If omitted, the default
   level is 1. Aborted connections are not logged to the error log unless the
   value is greater than 1. See Section 2.10, “Communication Errors and
   Aborted Connections”.

   Before MySQL 4.0.21 and 4.1.3, this is a boolean option, not an
   integer-valued option. Before 4.0, this option was named --warnings.

·  --low-priority-updates

   Give table-modifying operations (INSERT, REPLACE, DELETE, UPDATE) lower
   priority than selects. This can also be done via {INSERT | REPLACE | DELETE
   | UPDATE} LOW_PRIORITY ...  to lower the priority of only one query, or by
   SET LOW_PRIORITY_UPDATES=1 to change the priority in one thread. See
   Section 3.2, “Table Locking Issues”.

·  --memlock

   Lock the mysqld process in memory. This works on systems such as Solaris
   that support the mlockall() system call. This might help if you have a
   problem where the operating system is causing mysqld to swap on disk. Note
   that use of this option requires that you run the server as root, which is
   normally not a good idea for security reasons. See Section 5.5, “How to Run
   MySQL as a Normal User”.

·  --myisam-recover[=option[,option]...]]

   Set the MyISAM storage engine recovery mode. The option value is any
   combination of the values of DEFAULT, BACKUP, FORCE, or QUICK. If you
   specify multiple values, separate them by commas. You can also use a value
   of "" to disable this option. If this option is used, each time mysqld
   opens a MyISAM table, it checks whether the table is marked as crashed or
   wasn't closed properly. (The last option works only if you are running with
   external locking disabled.) If this is the case, mysqld runs a check on the
   table. If the table was corrupted, mysqld attempts to repair it.

   The following options affect how the repair works:

   ┌────────┬──────────────────────────────────────────────┐
   │Option  │ Description				   │
   ├────────┼──────────────────────────────────────────────┤
   │DEFAULT │ The same as not giving any		   │
   │	    │ option to					   │
   │	    │ --myisam-recover.				   │
   ├────────┼──────────────────────────────────────────────┤
   │BACKUP  │ If the data file was			   │
   │	    │ changed during recovery,			   │
   │	    │ save a backup of the			   │
   │	    │			    tbl_name.MYD	   │
   │	    │			    file		   │
   │	    │ as					   │
   │	    │			    tbl_name-datetime.BAK. │
   ├────────┼──────────────────────────────────────────────┤
   │FORCE   │ Run recovery even if we would lose more than │
   │	    │ one row from the				   │
   │	    │			    .MYD file.		   │
   ├────────┼──────────────────────────────────────────────┤
   │QUICK   │ do not check the rows in the table if there  │
   │	    │ are not any delete blocks.		   │
   └────────┴──────────────────────────────────────────────┘
   Before the server automatically repairs a table, it writes a note about the
   repair to the error log. If you want to be able to recover from most
   problems without user intervention, you should use the options
   BACKUP,FORCE. This forces a repair of a table even if some rows would be
   deleted, but it keeps the old data file as a backup so that you can later
   examine what happened.

   This option is available as of MySQL 3.23.25.

·  --ndb-connectstring=connect_string

   When using the NDB storage engine, it is possible to point out the
   management server that distributes the cluster configuration by setting the
   connect string option. See Section 4.4.2, “The Cluster connectstring”, for
   syntax.

·  --ndbcluster

   If the binary includes support for the NDB Cluster storage engine (from
   version 4.1.3, the MySQL-Max binaries are built with NDB Cluster enabled),
   this option enables the engine, which is disabled by default. Using the NDB
   Cluster storage engine is necessary for using MySQL Cluster. See
   Chapter 15, MySQL Cluster.

·  --new

   The --new option can be used to make the server behave as 4.1 in certain
   respects, easing a 4.0 to 4.1 upgrade:

   ·  Hexadecimal strings such as 0xFF are treated as strings by default
      rather than as numbers. (Works in 4.0.12 and up.)

   ·  TIMESTAMP is returned as a string with the format ´YYYY-MM-DD HH:MM:SS'.
      (Works in 4.0.13 and up.) See Chapter 11, Data Types.

   This option can be used to help you see how your applications behave in
   MySQL 4.1, without actually upgrading to 4.1.

·  --old-passwords

   Force the server to generate short (pre-4.1) password hashes for new
   passwords. This is useful for compatibility when the server must support
   older client programs. See Section 6.9, “Password Hashing as of MySQL 4.1”.

·  --old-protocol, -o

   Use the 3.20 protocol for compatibility with some very old clients.

·  --one-thread

   Only use one thread (for debugging under Linux). This option is available
   only if the server is built with debugging enabled. See Section 1,
   “Debugging a MySQL Server”.

·  --open-files-limit=count

   Change the number of file descriptors available to mysqld. If this option
   is not set or is set to 0, mysqld uses the value to reserve file
   descriptors with setrlimit(). If the value is 0, mysqld reserves
   max_connections×5 or max_connections + table_open_cache×2 files (whichever
   is larger). You should try increasing this value if mysqld gives you the
   error Too many open files.

·  --pid-file=path

   The pathname of the process ID file. This file is used by other programs
   such as mysqld_safe to determine the server's process ID.

·  --port=port_num, -P port_num

   The port number to use when listening for TCP/IP connections. The port
   number must be 1024 or higher unless the server is started by the root
   system user.

·  --safe-mode

   Skip some optimization stages.

·  --safe-show-database

   With this option, the SHOW DATABASES statement displays only the names of
   those databases for which the user has some kind of privilege. As of MySQL
   4.0.2, this option is deprecated and does not do anything (it is enabled by
   default), because there is a SHOW DATABASES privilege that can be used to
   control access to database names on a per-account basis. See Section 6.3,
   “Privileges Provided by MySQL”.

·  --safe-user-create

   If this option is enabled, a user cannot create new MySQL users by using
   the GRANT statement, if the user doesn't have the INSERT privilege for the
   mysql.user table or any column in the table.

·  --secure-auth

   Disallow authentication by clients that attempt to use accounts that have
   old (pre-4.1) passwords. This option is available as of MySQL 4.1.1.

·  --shared-memory

   Enable shared-memory connections by local clients. This option is available
   only on Windows. It was added in MySQL 4.1.0.

·  --shared-memory-base-name=name

   The name of shared memory to use for shared-memory connections. This option
   is available only on Windows. The default name is MYSQL. The name is case
   sensitive. This option was added in MySQL 4.1.0.

·  --skip-bdb

   Disable the BDB storage engine. This saves memory and might speed up some
   operations. Do not use this option if you require BDB tables.

·  --skip-concurrent-insert

   Turn off the ability to select and insert at the same time on MyISAM
   tables. (This is to be used only if you think you have found a bug in this
   feature.) See Section 3.3, “Concurrent Inserts”.

·  --skip-delay-key-write

   Ignore the DELAY_KEY_WRITE option for all tables. As of MySQL 4.0.3, you
   should use --delay-key-write=OFF instead. See Section 5.2, “Tuning Server
   Parameters”.

·  --skip-external-locking

   Do not use external locking (system locking). With external locking
   disabled, you must shut down the server to use myisamchk or isamchk. See
   Section 4.3, “MySQL Stability”. As of MySQL 3.23, you can use the CHECK
   TABLE and REPAIR TABLE statements to check and repair MyISAM tables. This
   option previously was named --skip-locking.

   External locking has been disabled by default since MySQL 4.0.

·  --skip-grant-tables

   This option causes the server not to use the privilege system at all, which
   gives anyone with access to the server unrestricted access to all
   databases. You can cause a running server to start using the grant tables
   again by executing mysqladmin flush-privileges or mysqladmin reload command
   from a system shell, or by issuing a MySQL FLUSH PRIVILEGES statement after
   connecting to the server. This option also suppresses loading of
   user-defined functions (UDFs).

·  --skip-host-cache

   Do not use the internal hostname cache for faster name-to-IP resolution.
   Instead, query the DNS server every time a client connects. See
   Section 5.5, “How MySQL Uses DNS”.

·  --skip-innodb

   Disable the InnoDB storage engine. This saves memory and disk space and
   might speed up some operations. Do not use this option if you require
   InnoDB tables.

·  --skip-isam

   Disable the ISAM storage engine. As of MySQL 4.1, ISAM is disabled by
   default, so this option applies only if the server was configured with
   support for ISAM. This option was added in MySQL 4.1.1.

·  --skip-merge

   Disable the MERGE storage engine. This option was added in MySQL 4.1.21. It
   can be used if the following behavior is undesirable: If a user has access
   to MyISAM table t, that user can create a MERGE table m that accesses t.
   However, if the user's privileges on t are subsequently revoked, the user
   can continue to access t by doing so through m.

·  --skip-name-resolve

   Do not resolve hostnames when checking client connections. Use only IP
   numbers. If you use this option, all Host column values in the grant tables
   must be IP numbers or localhost. See Section 5.5, “How MySQL Uses DNS”.

·  --skip-ndbcluster

   Disable the NDB Cluster storage engine. This is the default for binaries
   that were built with NDB Cluster storage engine support; the server
   allocates memory and other resources for this storage engine only if the
   --ndbcluster option is given explicitly. See Section 4.3, “Quick Test Setup
   of MySQL Cluster”, for an example of usage.

·  --skip-networking

   Do not listen for TCP/IP connections at all. All interaction with mysqld
   must be made via named pipes or shared memory (on Windows) or Unix socket
   files (on Unix). This option is highly recommended for systems where only
   local clients are allowed. See Section 5.5, “How MySQL Uses DNS”.

·  --skip-new

   do not use new, possibly wrong routines.

·  --skip-symlink

   This is the old form of --skip-symbolic-links, for use before MySQL 4.0.13.

·  --ssl*

   Options that begin with --ssl specify whether to allow clients to connect
   via SSL and indicate where to find SSL keys and certificates. See
   Section 7.7.3, “SSL Command Options”.

·  --standalone

   Available on Windows NT-based systems only; instructs the MySQL server not
   to run as a service.

·  --symbolic-links, --skip-symbolic-links

   Enable or disable symbolic link support. This option has different effects
   on Windows and Unix:

   ·  On Windows, enabling symbolic links allows you to establish a symbolic
      link to a database directory by creating a db_name.sym file that
      contains the path to the real directory. See Section 6.1.3, “Using
      Symbolic Links for Databases on Windows”.

   ·  On Unix, enabling symbolic links means that you can link a MyISAM index
      file or data file to another directory with the INDEX DIRECTORY or DATA
      DIRECTORY options of the CREATE TABLE statement. If you delete or rename
      the table, the files that its symbolic links point to also are deleted
      or renamed. See Section 6.1.2, “Using Symbolic Links for Tables on
      Unix”.

   This option was added in MySQL 4.0.13.

·  --skip-safemalloc

   If MySQL is configured with --with-debug=full, all MySQL programs check for
   memory overruns during each memory allocation and memory freeing operation.
   This checking is very slow, so for the server you can avoid it when you do
   not need it by using the --skip-safemalloc option.

·  --skip-show-database

   With this option, the SHOW DATABASES statement is allowed only to users who
   have the SHOW DATABASES privilege, and the statement displays all database
   names. Without this option, SHOW DATABASES is allowed to all users, but
   displays each database name only if the user has the SHOW DATABASES
   privilege or some privilege for the database. Note that any global
   privilege is considered a privilege for the database.

·  --skip-stack-trace

   do not write stack traces. This option is useful when you are running
   mysqld under a debugger. On some systems, you also must use this option to
   get a core file. See Section 1, “Debugging a MySQL Server”.

·  --skip-thread-priority

   Disable using thread priorities for faster response time.

·  --socket=path

   On Unix, this option specifies the Unix socket file to use when listening
   for local connections. The default value is /tmp/mysql.sock. On Windows,
   the option specifies the pipe name to use when listening for local
   connections that use a named pipe. The default value is MySQL (not case
   sensitive).

·  --sql-mode=value[,value[,value...]]

   Set the SQL mode. See the section called “SQL MODES”. This option was added
   in 3.23.41.

·  --temp-pool

   This option causes most temporary files created by the server to use a
   small set of names, rather than a unique name for each new file. This works
   around a problem in the Linux kernel dealing with creating many new files
   with different names. With the old behavior, Linux seems to “leak” memory,
   because it is being allocated to the directory entry cache rather than to
   the disk cache.

·  --transaction-isolation=level

   Sets the default transaction isolation level. The level value can be
   READ-UNCOMMITTED, READ-COMMITTED, REPEATABLE-READ, or SERIALIZABLE. See
   Section 4.6, “SET TRANSACTION Syntax”.

·  --tmpdir=path, -t path

   The path of the directory to use for creating temporary files. It might be
   useful if your default /tmp directory resides on a partition that is too
   small to hold temporary tables. Starting from MySQL 4.1.0, this option
   accepts several paths that are used in round-robin fashion. Paths should be
   separated by colon characters (‘:’) on Unix and semicolon characters (‘;’)
   on Windows, NetWare, and OS/2. If the MySQL server is acting as a
   replication slave, you should not set --tmpdir to point to a directory on a
   memory-based filesystem or to a directory that is cleared when the server
   host restarts. For more information about the storage location of temporary
   files, see Section 4.4, “Where MySQL Stores Temporary Files”. A replication
   slave needs some of its temporary files to survive a machine restart so
   that it can replicate temporary tables or LOAD DATA INFILE operations. If
   files in the temporary file directory are lost when the server restarts,
   replication fails.

·  --user={user_name|user_id}, -u {user_name|user_id}

   Run the mysqld server as the user having the name user_name or the numeric
   user ID user_id. (“User” in this context refers to a system login account,
   not a MySQL user listed in the grant tables.)

   This option is mandatory when starting mysqld as root. The server changes
   its user ID during its startup sequence, causing it to run as that
   particular user rather than as root. See Section 5.1, “General Security
   Guidelines”.

   Starting from MySQL 3.23.56 and 4.0.12: To avoid a possible security hole
   where a user adds a --user=root option to a my.cnf file (thus causing the
   server to run as root), mysqld uses only the first --user option specified
   and produces a warning if there are multiple --user options. Options in
   /etc/my.cnf and $MYSQL_HOME/my.cnf are processed before command-line
   options, so it is recommended that you put a --user option in /etc/my.cnf
   and specify a value other than root. The option in /etc/my.cnf is found
   before any other --user options, which ensures that the server runs as a
   user other than root, and that a warning results if any other --user option
   is found.

·  --version, -V

   Display version information and exit.

As of MySQL 4.0, you can assign a value to a server system variable by using
an option of the form --var_name=value. For example, --key_buffer_size=32M
sets the key_buffer_size variable to a value of 32MB.

Note that when you assign a value to a variable, MySQL might automatically
correct the value to stay within a given range, or adjust the value to the
closest allowable value if only certain values are allowed.

If you want to restrict the maximum value to which a variable can be set at
runtime with SET, you can define this by using the --maximum-var_name=value
command-line option.

It is also possible to set variables by using --set-variable=var_name=value or
--var_name=value syntax.  This syntax is deprecated as of MySQL 4.0.

You can change the values of most system variables for a running server with
the SET statement. See Section 5.3, “SET Syntax”.

the section called “SYSTEM VARIABLES”, provides a full description for all
variables, and additional information for setting them at server startup and
runtime.  Section 5.2, “Tuning Server Parameters”, includes information on
optimizing the server by tuning system variables.

SYSTEM VARIABLES
       The mysql server maintains many system variables that indicate how it
       is configured. Each system variable has a default value. System
       variables can be set at server startup using options on the command
       line or in an option file. As of MySQL 4.0.3, most of them can be
       changed dynamically while the server is running by means of the SET
       statement, which enables you to modify operation of the server without
       having to stop and restart it. You can refer to system variable values
       in expressions.

       There are several ways to see the names and values of system variables:

       ·  To see the values that a server will use based on its compiled-in
	  defaults and any option files that it reads, use this command (omit
	  --verbose before MySQL 4.1.1):

	  mysqld --verbose --help

       ·  To see the values that a server will use based on its compiled-in
	  defaults, ignoring the settings in any option files, use this
	  command (omit --verbose before MySQL 4.1.1):

	  mysqld --no-defaults --verbose --help

       ·  To see the current values used by a running server, use the SHOW
	  VARIABLES statement.

       This section provides a description of each system variable. Variables
       with no version indicated have been present since at least MySQL 3.22.

       For additional system variable information, see these sections:

       ·  the section called “USING SYSTEM VARIABLES”, discusses the syntax
	  for setting and displaying system variable values.

       ·  the section called “Dynamic System Variables”, lists the variables
	  that can be set at runtime.

       ·  Information on tuning sytem variables can be found in Section 5.2,
	  “Tuning Server Parameters”.

       ·  Section 2.5, “InnoDB Startup Options and System Variables”, lists
	  InnoDB system variables.

       Note: Some of the following variable descriptions refer to “enabling”
       or “disabling” a variable. These variables can be enabled with the SET
       statement by setting them to ON or 1, or disabled by setting them to
       OFF or 0. However, to set such a variable on the command line or in an
       option file, you must set it to 1 or 0; setting it to ON or OFF will
       not work. For example, on the command line, --delay_key_write=1 works
       but --delay_key_write=ON does not.

       Values for buffer sizes, lengths, and stack sizes are given in bytes
       unless otherwise specified.

       ·  ansi_mode

	  This is ON if mysqld was started with --ansi. See Section 9.3,
	  “Running MySQL in ANSI Mode”. This variable was added in MySQL
	  3.23.6 and removed in 3.23.41. See the description for sql_mode.

       ·  back_log

	  The number of outstanding connection requests MySQL can have. This
	  comes into play when the main MySQL thread gets very many connection
	  requests in a very short time. It then takes some time (although
	  very little) for the main thread to check the connection and start a
	  new thread. The back_log value indicates how many requests can be
	  stacked during this short time before MySQL momentarily stops
	  answering new requests. You need to increase this only if you expect
	  a large number of connections in a short period of time.

	  In other words, this value is the size of the listen queue for
	  incoming TCP/IP connections. Your operating system has its own limit
	  on the size of this queue. The manual page for the Unix listen()
	  system call should have more details. Check your OS documentation
	  for the maximum value for this variable.  back_log cannot be set
	  higher than your operating system limit.

       ·  basedir

	  The MySQL installation base directory. This variable can be set with
	  the --basedir option.

       ·  bdb_cache_size

	  The size of the buffer that is allocated for caching indexes and
	  rows for BDB tables. If you do not use BDB tables, you should start
	  mysqld with --skip-bdb to not allocate memory for this cache. This
	  variable was added in MySQL 3.23.14.

       ·  bdb_home

	  The base directory for BDB tables. This should be assigned the same
	  value as the datadir variable. This variable was added in MySQL
	  3.23.14.

       ·  bdb_log_buffer_size

	  The size of the buffer that is allocated for caching indexes and
	  rows for BDB tables. If you do not use BDB tables, you should set
	  this to 0 or start mysqld with --skip-bdb in order not to allocate
	  memory for this cache. This variable was added in MySQL 3.23.31.

       ·  bdb_logdir

	  The directory where the BDB storage engine writes its log files.
	  This variable can be set with the --bdb-logdir option. This variable
	  was added in MySQL 3.23.14.

       ·  bdb_max_lock

	  The maximum number of locks that can be active for a BDB table
	  (10,000 by default). You should increase this value if errors such
	  as the following occur when you perform long transactions or when
	  mysqld has to examine many rows to calculate a query:

	  bdb: Lock table is out of available locks
	  Got error 12 from ...
       This variable was added in MySQL 3.23.29.

       ·  bdb_shared_data

	  This is ON if you are using --bdb-shared-data to start Berkeley DB
	  in multi-process mode. (Do not use DB_PRIVATE when initializing
	  Berkeley DB.) This variable was added in MySQL 3.23.29.

       ·  bdb_tmpdir

	  The BDB temporary file directory. This variable was added in MySQL
	  3.23.14.

       ·  bdb_version

	  See the description for version_bdb.

       ·  binlog_cache_size

	  The size of the cache to hold the SQL statements for the binary log
	  during a transaction. A binary log cache is allocated for each
	  client if the server supports any transactional storage engines and,
	  starting from MySQL 4.1.2, if the server has the binary log enabled
	  (--log-bin option). If you often use large, multiple-statement
	  transactions, you can increase this cache size to get more
	  performance. The Binlog_cache_use and Binlog_cache_disk_use status
	  variables can be useful for tuning the size of this variable. This
	  variable was added in MySQL 3.23.29. See Section 10.4, “The Binary
	  Log”.

       ·  bulk_insert_buffer_size

	  MyISAM uses a special tree-like cache to make bulk inserts faster
	  for INSERT ... SELECT, INSERT ... VALUES (...), (...), ..., and LOAD
	  DATA INFILE when adding data to non-empty tables. This variable
	  limits the size of the cache tree in bytes per thread. Setting it to
	  0 disables this optimization. The default value is 8MB. This
	  variable was added in MySQL 4.0.3. This variable previously was
	  named myisam_bulk_insert_tree_size.

       ·  character_set

	  The default character set. This variable was added in MySQL 3.23.3,
	  then removed in MySQL 4.1.1 and replaced by the various
	  character_set_xxx variables.

       ·  character_set_client

	  The character set for statements that arrive from the client. This
	  variable was added in MySQL 4.1.1.

       ·  character_set_connection

	  The character set used for literals that do not have a character set
	  introducer and for number-to-string conversion. This variable was
	  added in MySQL 4.1.1.

       ·  character_set_database

	  The character set used by the default database. The server sets this
	  variable whenever the default database changes. If there is no
	  default database, the variable has the same value as
	  character_set_server. This variable was added in MySQL 4.1.1.

       ·  character_set_results

	  The character set used for returning query results to the client.
	  This variable was added in MySQL 4.1.1.

       ·  character_set_server

	  The server default character set. This variable was added in MySQL
	  4.1.1.

       ·  character_set_system

	  The character set used by the server for storing identifiers. The
	  value is always utf8. This variable was added in MySQL 4.1.1.

       ·  character_sets

	  The supported character sets. This variable was added in MySQL
	  3.23.15 and removed in MySQL 4.1.1. (Use SHOW CHARACTER SET for a
	  list of character sets.)

       ·  character_sets_dir

	  The directory where character sets are installed. This variable was
	  added in MySQL 4.1.2.

       ·  collation_connection

	  The collation of the connection character set. This variable was
	  added in MySQL 4.1.1.

       ·  collation_database

	  The collation used by the default database. The server sets this
	  variable whenever the default database changes. If there is no
	  default database, the variable has the same value as
	  collation_server. This variable was added in MySQL 4.1.1.

       ·  collation_server

	  The server default collation. This variable was added in MySQL
	  4.1.1.

       ·  concurrent_insert

	  If ON (the default), MySQL allows INSERT and SELECT statements to
	  run concurrently for MyISAM tables that have no free blocks in the
	  middle. You can turn this option off by starting mysqld with --safe
	  or --skip-new. This variable was added in MySQL 3.23.7.

	  See also Section 3.3, “Concurrent Inserts”.

       ·  connect_timeout

	  The number of seconds that the mysqld server waits for a connect
	  packet before responding with Bad handshake.

       ·  convert_character_set

	  The current character set mapping that was set by SET CHARACTER SET.
	  This variable was removed in MySQL 4.1.

       ·  datadir

	  The MySQL data directory. This variable can be set with the
	  --datadir option.

       ·  date_format

	  This variable is not implemented.

       ·  datetime_format

	  This variable is not implemented.

       ·  default_week_format

	  The default mode value to use for the WEEK() function. See
	  Section 5, “Date and Time Functions”. This variable is available as
	  of MySQL 4.0.14.

       ·  delay_key_write

	  This option applies only to MyISAM tables. It can have one of the
	  following values to affect handling of the DELAY_KEY_WRITE table
	  option that can be used in CREATE TABLE statements.

	  ┌───────┬───────────────────────────────────────┐
	  │Option │ Description				  │
	  ├───────┼───────────────────────────────────────┤
	  │OFF	  │ DELAY_KEY_WRITE is			  │
	  │	  │ ignored.				  │
	  ├───────┼───────────────────────────────────────┤
	  │ON	  │ MySQL honors any			  │
	  │	  │ DELAY_KEY_WRITE option		  │
	  │	  │ specified in			  │
	  │	  │			  CREATE	  │
	  │	  │ TABLE statements. This		  │
	  │	  │			  is		  │
	  │	  │ the default value.			  │
	  ├───────┼───────────────────────────────────────┤
	  │ALL	  │ All new opened tables are		  │
	  │	  │ treated as if they were		  │
	  │	  │ created with the			  │
	  │	  │			  DELAY_KEY_WRITE │
	  │	  │ option enabled.			  │
	  └───────┴───────────────────────────────────────┘
	  If DELAY_KEY_WRITE is enabled for a table, the key buffer is not
	  flushed for the table on every index update, but only when the table
	  is closed. This speeds up writes on keys a lot, but if you use this
	  feature, you should add automatic checking of all MyISAM tables by
	  starting the server with the --myisam-recover option (for example,
	  --myisam-recover=BACKUP,FORCE). See the section called “COMMAND
	  OPTIONS”, and Section 1.1, “MyISAM Startup Options”.

	  Note that enabling external locking with --external-locking offers
	  no protection against index corruption for tables that use delayed
	  key writes.

	  This variable was added in MySQL 3.23.8.

       ·  delayed_insert_limit

	  After inserting delayed_insert_limit delayed rows, the INSERT
	  DELAYED handler thread checks whether there are any SELECT
	  statements pending. If so, it allows them to execute before
	  continuing to insert delayed rows.

       ·  delayed_insert_timeout

	  How many seconds an INSERT DELAYED handler thread should wait for
	  INSERT statements before terminating.

       ·  delayed_queue_size

	  This is a per-table limit on the number of rows to queue when
	  handling INSERT DELAYED statements. If the queue becomes full, any
	  client that issues an INSERT DELAYED statement waits until there is
	  room in the queue again.

       ·  expire_logs_days

	  The number of days for automatic binary log removal. The default is
	  0, which means “no automatic removal.”  Possible removals happen at
	  startup and at binary log rotation. This variable was added in MySQL
	  4.1.0.

       ·  flush

	  If ON, the server flushes (synchronizes) all changes to disk after
	  each SQL statement. Normally, MySQL does a write of all changes to
	  disk only after each SQL statement and lets the operating system
	  handle the synchronizing to disk. See Section 4.2, “What to Do If
	  MySQL Keeps Crashing”. This variable is set to ON if you start
	  mysqld with the --flush option. This variable was added in MySQL
	  3.22.9.

       ·  flush_time

	  If this is set to a non-zero value, all tables are closed every
	  flush_time seconds to free up resources and synchronize unflushed
	  data to disk. We recommend that this option be used only on Windows
	  9x or Me, or on systems with minimal resources. This variable was
	  added in MySQL 3.22.18.

       ·  ft_boolean_syntax

	  The list of operators supported by boolean full-text searches
	  performed using IN BOOLEAN MODE. See Section 7.1, “Boolean Full-Text
	  Searches”. This variable was added as a read-only variable in MySQL
	  4.0.1. It can be modified as of MySQL 4.1.2.

	  The default variable value is ´+ -><()~*:""&|'. The rules for
	  changing the value are as follows:

	  ·  Operator function is determined by position within the string.

	  ·  The replacement value must be 14 characters.

	  ·  Each character must be an ASCII non-alphanumeric character.

	  ·  Either the first or second character must be a space.

	  ·  No duplicates are allowed except the phrase quoting operators in
	     positions 11 and 12. These two characters are not required to be
	     the same, but they are the only two that may be.

	  ·  Positions 10, 13, and 14 (which by default are set to ‘:’, ‘&’,
	     and ‘|’) are reserved for future extensions.

       ·  ft_max_word_len

	  The maximum length of the word to be included in a FULLTEXT index.
	  This variable was added in MySQL 4.0.0.

	  Note: FULLTEXT indexes must be rebuilt after changing this variable.
	  Use REPAIR TABLE tbl_name QUICK.

       ·  ft_min_word_len

	  The minimum length of the word to be included in a FULLTEXT index.
	  This variable was added in MySQL 4.0.0.

	  Note: FULLTEXT indexes must be rebuilt after changing this variable.
	  Use REPAIR TABLE tbl_name QUICK.

       ·  ft_query_expansion_limit

	  The number of top matches to use for full-text searches performed
	  using WITH QUERY EXPANSION. This variable was added in MySQL 4.1.1.

       ·  ft_stopword_file

	  The file from which to read the list of stopwords for full-text
	  searches. All the words from the file are used; comments are not
	  honored. By default, a built-in list of stopwords is used (as
	  defined in the myisam/ft_static.c file). Setting this variable to
	  the empty string ('') disables stopword filtering. This variable was
	  added in MySQL 4.0.10.

	  Note: FULLTEXT indexes must be rebuilt after changing this variable
	  or the contents of the stopword file. Use REPAIR TABLE tbl_name
	  QUICK.

       ·  group_concat_max_len

	  The maximum allowed result length for the GROUP_CONCAT() function.
	  The default is 1024. This variable was added in MySQL 4.1.0.

       ·  have_archive

	  YES if mysqld supports ARCHIVE tables, NO if not. This variable was
	  added in MySQL 4.1.3.

       ·  have_bdb

	  YES if mysqld supports BDB tables.  DISABLED if --skip-bdb is used.
	  This variable was added in MySQL 3.23.30.

       ·  have_blackhole_engine

	  YES if mysqld supports BLACKHOLE tables, NO if not. This variable
	  was added in MySQL 4.1.11.

       ·  have_compress

	  YES if the zlib compression library is available to the server, NO
	  if not. If not, the COMPRESS() and UNCOMPRESS() functions cannot be
	  used. This variable was added in MySQL 4.1.1.

       ·  have_crypt

	  YES if the crypt() system call is available to the server, NO if
	  not. If not, the ENCRYPT() function cannot be used. This variable
	  was added in MySQL 4.0.10.

       ·  have_csv

	  YES if mysqld supports ARCHIVE tables, NO if not. This variable was
	  added in MySQL 4.1.4.

       ·  have_example_engine

	  YES if mysqld supports EXAMPLE tables, NO if not. This variable was
	  added in MySQL 4.1.4.

       ·  have_geometry

	  YES if the server supports spatial data types, NO if not. This
	  variable was added in MySQL 4.1.3.

       ·  have_innodb

	  YES if mysqld supports InnoDB tables.	 DISABLED if --skip-innodb is
	  used. This variable was added in MySQL 3.23.37.

       ·  have_isam

	  YES if mysqld supports ISAM tables.  DISABLED if --skip-isam is
	  used. This variable was added in MySQL 3.23.30.

       ·  have_ndbcluster

	  YES if mysqld supports NDB Cluster tables.  DISABLED if
	  --skip-ndbcluster is used. This variable was added in MySQL 4.1.2.

       ·  have_openssl

	  YES if mysqld supports SSL (encryption) connections, NO if not. This
	  variable was added in MySQL 3.23.43.

       ·  have_query_cache

	  YES if mysqld supports the query cache, NO if not. This variable was
	  added in MySQL 4.0.2.

       ·  have_raid

	  YES if mysqld supports the RAID option, NO if not. This variable was
	  added in MySQL 3.23.30.

       ·  have_rtree_keys

	  YES if RTREE indexes are available, NO if not. (These are used for
	  spatial indexes in MyISAM tables.) This variable was added in MySQL
	  4.1.3.

       ·  have_symlink

	  YES if symbolic link support is enabled, NO if not. This is required
	  on Unix for support of the DATA DIRECTORY and INDEX DIRECTORY table
	  options, and on Windows for support of data directory symlinks.

	  This variable was added in MySQL 4.0.0.

       ·  init_connect

	  A string to be executed by the server for each client that connects.
	  The string consists of one or more SQL statements. To specify
	  multiple statements, separate them by semicolon characters. For
	  example, each client begins by default with autocommit mode enabled.
	  There is no global system variable to specify that autocommit should
	  be disabled by default, but init_connect can be used to achieve the
	  same effect:

	  SET GLOBAL init_connect='SET AUTOCOMMIT=0';
       This variable can also be set on the command line or in an option file.
       To set the variable as just shown using an option file, include these
       lines:

	  [mysqld]
	  init_connect='SET AUTOCOMMIT=0'
       Note that the content of init_connect is not executed for users that
       have the SUPER privilege. This is done so that an erroneous value for
       init_connect does not prevent all clients from connecting. For example,
       the value might contain a statement that has a syntax error, thus
       causing client connections to fail. Not executing init_connect for
       users that have the SUPER privilege enables them to open a connection
       and fix the init_connect value.

       This variable was added in MySQL 4.1.2.

       ·  init_file

	  The name of the file specified with the --init-file option when you
	  start the server. This should be a file containing SQL statements
	  that you want the server to execute when it starts. Each statement
	  must be on a single line and should not include comments. This
	  variable was added in MySQL 3.23.2.

       ·  init_slave

	  This variable is similar to init_connect, but is a string to be
	  executed by a slave server each time the SQL thread starts. The
	  format of the string is the same as for the init_connect variable.
	  This variable was added in MySQL 4.1.2.

       ·  innodb_xxx

	  InnoDB system variables are listed in Section 2.5, “InnoDB Startup
	  Options and System Variables”.

       ·  interactive_timeout

	  The number of seconds the server waits for activity on an
	  interactive connection before closing it. An interactive client is
	  defined as a client that uses the CLIENT_INTERACTIVE option to
	  mysql_real_connect(). See also wait_timeout.

       ·  join_buffer_size

	  The size of the buffer that is used for joins that do not use
	  indexes and thus perform full table scans. Normally, the best way to
	  get fast joins is to add indexes. Increase the value of
	  join_buffer_size to get a faster full join when adding indexes is
	  not possible. One join buffer is allocated for each full join
	  between two tables. For a complex join between several tables for
	  which indexes are not used, multiple join buffers might be
	  necessary.

       ·  key_buffer_size

	  Index blocks for MyISAM and ISAM tables are buffered and are shared
	  by all threads.  key_buffer_size is the size of the buffer used for
	  index blocks. The key buffer is also known as the key cache.

	  The maximum allowable setting for key_buffer_size is 4GB. The
	  effective maximum size might be less, depending on your available
	  physical RAM and per-process RAM limits imposed by your operating
	  system or hardware platform.

	  Increase the value to get better index handling (for all reads and
	  multiple writes) to as much as you can afford. Using a value that is
	  25% of total memory on a machine that mainly runs MySQL is quite
	  common. However, if you make the value too large (for example, more
	  than 50% of your total memory) your system might start to page and
	  become extremely slow. MySQL relies on the operating system to
	  perform filesystem caching for data reads, so you must leave some
	  room for the filesystem cache. Consider also the memory requirements
	  of other storage engines.

	  For even more speed when writing many rows at the same time, use
	  LOCK TABLES. See Section 2.13, “Speed of INSERT Statements”.

	  You can check the performance of the key buffer by issuing a SHOW
	  STATUS statement and examining the Key_read_requests, Key_reads,
	  Key_write_requests, and Key_writes status variables. (See
	  Section 5.4, “SHOW Syntax”.) The Key_reads/Key_read_requests ratio
	  should normally be less than 0.01. The Key_writes/Key_write_requests
	  ratio is usually near 1 if you are using mostly updates and deletes,
	  but might be much smaller if you tend to do updates that affect many
	  rows at the same time or if you are using the DELAY_KEY_WRITE table
	  option.

	  The fraction of the key buffer in use can be determined using
	  key_buffer_size in conjunction with the Key_blocks_unused status
	  variable and the buffer block size. From MySQL 4.1.1 on, the buffer
	  block size is available from the key_cache_block_size server
	  variable. The fraction of the buffer in use is:

	  1 - ((Key_blocks_unused × key_cache_block_size) / key_buffer_size)
       This value is an approximation because some space in the key buffer may
       be allocated internally for administrative structures.

       Before MySQL 4.1.1, key cache blocks are 1024 bytes, and before MySQL
       4.1.2, Key_blocks_unused is unavailable. The Key_blocks_used variable
       can be used as follows to determine the fraction of the key buffer in
       use:

	  (Key_blocks_used × 1024) / key_buffer_size
       However, Key_blocks_used indicates the maximum number of blocks that
       have ever been in use at once, so this formula does not necessarily
       represent the current fraction of the buffer that is in use.

       As of MySQL 4.1, it is possible to create multiple MyISAM key caches.
       The size limit of 4GB applies to each cache individually, not as a
       group. See Section 4.6, “The MyISAM Key Cache”.

       ·  key_cache_age_threshold

	  This value controls the demotion of buffers from the hot sub-chain
	  of a key cache to the warm sub-chain. Lower values cause demotion to
	  happen more quickly. The minimum value is 100. The default value is
	  300. This variable was added in MySQL 4.1.1. See Section 4.6, “The
	  MyISAM Key Cache”.

       ·  key_cache_block_size

	  The size in bytes of blocks in the key cache. The default value is
	  1024. This variable was added in MySQL 4.1.1. See Section 4.6, “The
	  MyISAM Key Cache”.

       ·  key_cache_division_limit

	  The division point between the hot and warm sub-chains of the key
	  cache buffer chain. The value is the percentage of the buffer chain
	  to use for the warm sub-chain. Allowable values range from 1 to 100.
	  The default value is 100. This variable was added in MySQL 4.1.1.
	  See Section 4.6, “The MyISAM Key Cache”.

       ·  language

	  The language used for error messages.

       ·  large_file_support

	  Whether mysqld was compiled with options for large file support.
	  This variable was added in MySQL 3.23.28.

       ·  large_pages

	  Whether large page support is enabled. This variable was added in
	  MySQL 5.0.3.

       ·  license

	  The type of license the server has. This variable was added in MySQL
	  4.0.19.

       ·  local_infile

	  Whether LOCAL is supported for LOAD DATA INFILE statements. See
	  Section 5.4, “Security Issues with LOAD DATA LOCAL”. This variable
	  was added in MySQL 4.0.3.

       ·  locked_in_memory

	  Whether mysqld was locked in memory with --memlock. This variable
	  was added in MySQL 3.23.25.

       ·  log

	  Whether logging of all statements to the general query log is
	  enabled. See Section 10.2, “The General Query Log”.

       ·  log_bin

	  Whether the binary log is enabled. This variable was added in MySQL
	  3.23.14. See Section 10.4, “The Binary Log”.

       ·  log_error

	  The location of the error log. This variable was added in MySQL
	  4.0.10.

       ·  log_slave_updates

	  Whether updates received by a slave server from a master server
	  should be logged to the slave's own binary log. Binary logging must
	  be enabled on the slave for this variable to have any effect. This
	  variable was added in MySQL 3.23.17. See Section 8, “Replication
	  Startup Options”.

       ·  log_slow_queries

	  Whether slow queries should be logged.  “Slow” is determined by the
	  value of the long_query_time variable. This variable was added in
	  MySQL 4.0.2. See Section 10.5, “The Slow Query Log”.

       ·  log_update

	  Whether the update log is enabled. This variable was added in MySQL
	  3.22.18. Note that the binary log is preferable to the update log,
	  which is unavailable as of MySQL 5.0. See Section 10.3, “The Update
	  Log”.

       ·  log_warnings

	  Whether to produce additional warning messages. This variable was
	  added in MySQL 4.0.3. It is enabled by default as of MySQL 4.0.19
	  and 4.1.2. As of MySQL 4.0.21 and 4.1.3, the variable can take
	  values greater than 1 and aborted connections are not logged to the
	  error log unless the value is greater than 1.

       ·  long_query_time

	  If a query takes longer than this many seconds, the server
	  increments the Slow_queries status variable. If you are using the
	  --log-slow-queries option, the query is logged to the slow query log
	  file. This value is measured in real time, not CPU time, so a query
	  that is under the threshold on a lightly loaded system might be
	  above the threshold on a heavily loaded one. The minimum value is 1.
	  The default is 10. See Section 10.5, “The Slow Query Log”.

       ·  low_priority_updates

	  If set to 1, all INSERT, UPDATE, DELETE, and LOCK TABLE WRITE
	  statements wait until there is no pending SELECT or LOCK TABLE READ
	  on the affected table. This variable previously was named
	  sql_low_priority_updates. It was added in MySQL 3.22.5.

       ·  lower_case_file_system

	  This variable describes the case sensitivity of filenames on the
	  filesystem where the data directory is located.  OFF means filenames
	  are case sensitive, ON means they are not case sensitive. This
	  variable was added in MySQL 4.0.19.

       ·  lower_case_table_names

	  If set to 1 table names are stored in lowercase on disk and table
	  name comparisons are not case sensitive. This variable was added in
	  MySQL 3.23.6. If set to 2 (new in 4.0.18), table names are stored as
	  given but compared in lowercase. From MySQL 4.0.2, this option also
	  applies to database names. From 4.1.1, it also applies to table
	  aliases. See Section 2.2, “Identifier Case Sensitivity”.

	  Note: If you are using InnoDB tables, you should set this variable
	  to 1 on all platforms to force names to be converted to lowercase.

	  You should not set this variable to 0 if you are running MySQL on a
	  system that does not have case-sensitive filenames (such as Windows
	  or Mac OS X).	 New in 4.0.18: If this variable is not set at startup
	  and the filesystem on which the data directory is located does not
	  have case-sensitive filenames, MySQL automatically sets
	  lower_case_table_names to 2.

       ·  max_allowed_packet

	  The maximum size of one packet or any generated/intermediate string.

	  The packet message buffer is initialized to net_buffer_length bytes,
	  but can grow up to max_allowed_packet bytes when needed. This value
	  by default is small, to catch large (possibly incorrect) packets.

	  You must increase this value if you are using large BLOB columns or
	  long strings. It should be as big as the largest BLOB you want to
	  use. The protocol limit for max_allowed_packet is 16MB before MySQL
	  4.0 and 1GB thereafter.

       ·  max_binlog_cache_size

	  If a multiple-statement transaction requires more than this amount
	  of memory, the server generates a Multi-statement transaction
	  required more than 'max_binlog_cache_size' bytes of storage error.
	  This variable was added in MySQL 3.23.29.

       ·  max_binlog_size

	  If a write to the binary log causes the current log file size to
	  exceed the value of this variable, the server rotates the binary
	  logs (closes the current file and opens the next one). You cannot
	  set this variable to more than 1GB or to less than 4096 bytes. (The
	  minimum before MYSQL 4.0.14 is 1024 bytes.) The default value is
	  1GB. This variable was added in MySQL 3.23.33.

	  A transaction is written in one chunk to the binary log, so it is
	  never split between several binary logs. Therefore, if you have big
	  transactions, you might see binary logs larger than max_binlog_size.

	  If max_relay_log_size is 0, the value of max_binlog_size applies to
	  relay logs as well.  max_relay_log_size was added in MySQL 4.0.14.

       ·  max_connect_errors

	  If there are more than this number of interrupted connections from a
	  host, that host is blocked from further connections. You can unblock
	  blocked hosts with the FLUSH HOSTS statement.

       ·  max_connections

	  The number of simultaneous client connections allowed. Increasing
	  this value increases the number of file descriptors that mysqld
	  requires. See Section 4.8, “How MySQL Opens and Closes Tables”, for
	  comments on file descriptor limits. See also Section 2.6, “Too many
	  connections”.

       ·  max_delayed_threads

	  Do not start more than this number of threads to handle INSERT
	  DELAYED statements. If you try to insert data into a new table after
	  all INSERT DELAYED threads are in use, the row is inserted as if the
	  DELAYED attribute wasn't specified. If you set this to 0, MySQL
	  never creates a thread to handle DELAYED rows; in effect, doing so
	  disables DELAYED entirely. This variable was added in MySQL 3.23.0.

       ·  max_error_count

	  The maximum number of error, warning, and note messages to be stored
	  for display by the SHOW ERRORS or SHOW WARNINGS statements. This
	  variable was added in MySQL 4.1.0.

       ·  max_heap_table_size

	  This variable sets the maximum size to which MEMORY (HEAP) tables
	  are allowed to grow. The value of the variable is used to calculate
	  MEMORY table MAX_ROWS values. Setting this variable has no effect on
	  any existing MEMORY table, unless the table is re-created with a
	  statement such as CREATE TABLE, or altered with ALTER TABLE or
	  TRUNCATE TABLE. This variable was added in MySQL 3.23.0.

       ·  max_insert_delayed_threads

	  This variable is a synonym for max_delayed_threads. It was added in
	  MySQL 4.0.19.

       ·  max_join_size

	  Do not allow SELECT statements that probably need to examine more
	  than max_join_size rows (for single-table statements) or row
	  combinations (for multiple-table statements) or that are likely to
	  do more than max_join_size disk seeks. By setting this value, you
	  can catch SELECT statements where keys are not used properly and
	  that would probably take a long time. Set it if your users tend to
	  perform joins that lack a WHERE clause, that take a long time, or
	  that return millions of rows.

	  Setting this variable to a value other than DEFAULT resets the value
	  of SQL_BIG_SELECTS to 0. If you set the SQL_BIG_SELECTS value again,
	  the max_join_size variable is ignored.

	  If a query result is in the query cache, no result size check is
	  performed, because the result has previously been computed and it
	  does not burden the server to send it to the client.

	  This variable previously was named sql_max_join_size.

       ·  max_length_for_sort_data

	  The cutoff on the size of index values that determines which
	  filesort algorithm to use. See Section 2.9, “ORDER BY Optimization”.
	  This variable was added in MySQL 4.1.1

       ·  max_prepared_stmt_count

	  This variable limits the total number of prepared statements in the
	  server. It can be used in environments where there is the potential
	  for denial-of-service attacks based on running the server out of
	  memory by preparing huge numbers of statements. The default value is
	  16,382. The allowable range of values is from 0 to 1 million. If the
	  value is set lower than the current number of prepared statements,
	  existing statements are not affected and can be used, but no new
	  statements can be prepared until the current number drops below the
	  limit. This variable was added in MySQL 4.1.19.

       ·  max_relay_log_size

	  If a write by a replication slave to its relay log causes the
	  current log file size to exceed the value of this variable, the
	  slave rotates the relay logs (closes the current file and opens the
	  next one). If max_relay_log_size is 0, the server uses
	  max_binlog_size for both the binary log and the relay log. If
	  max_relay_log_size is greater than 0, it constrains the size of the
	  relay log, which enables you to have different sizes for the two
	  logs. You must set max_relay_log_size to between 4096 bytes and 1GB
	  (inclusive), or to 0. The default value is 0. This variable was
	  added in MySQL 4.0.14. See Section 3, “Replication Implementation
	  Details”.

       ·  max_seeks_for_key

	  Limit the assumed maximum number of seeks when looking up rows based
	  on a key. The MySQL optimizer assumes that no more than this number
	  of key seeks are required when searching for matching rows in a
	  table by scanning an index, regardless of the actual cardinality of
	  the index (see Section 5.4.11, “SHOW INDEX Syntax”). By setting this
	  to a low value (say, 100), you can force MySQL to prefer indexes
	  instead of table scans.

	  This variable was added in MySQL 4.0.14.

       ·  max_sort_length

	  The number of bytes to use when sorting BLOB or TEXT values. Only
	  the first max_sort_length bytes of each value are used; the rest are
	  ignored.

       ·  max_tmp_tables

	  The maximum number of temporary tables a client can keep open at the
	  same time. (This option does not yet do anything.)

       ·  max_user_connections

	  The maximum number of simultaneous connections allowed to any given
	  MySQL account. A value of 0 means “no limit.”	 This variable was
	  added in MySQL 3.23.34.

	  This variable has only a global form.

       ·  max_write_lock_count

	  After this many write locks, allow some pending read lock requests
	  to be processed in between. This variable was added in MySQL 3.23.7.

       ·  myisam_data_pointer_size

	  The default pointer size in bytes, to be used by CREATE TABLE for
	  MyISAM tables when no MAX_ROWS option is specified. This variable
	  cannot be less than 2 or larger than 7. The default value is 4. This
	  variable was added in MySQL 4.1.2. See Section 2.11, “The table is
	  full”.

       ·  myisam_max_extra_sort_file_size

	  If the temporary file used for fast MyISAM index creation would be
	  larger than using the key cache by the amount specified here, prefer
	  the key cache method. This is mainly used to force long character
	  keys in large tables to use the slower key cache method to create
	  the index. This variable was added in MySQL 3.23.37.	Note: The
	  value is given in megabytes before 4.0.3 and in bytes thereafter.

       ·  myisam_max_sort_file_size

	  The maximum size of the temporary file that MySQL is allowed to use
	  while re-creating a MyISAM index (during REPAIR TABLE, ALTER TABLE,
	  or LOAD DATA INFILE). If the file size would be larger than this
	  value, the index is created using the key cache instead, which is
	  slower. This variable was added in MySQL 3.23.37.  Note: The value
	  is given in megabytes before 4.0.3 and in bytes thereafter.

	  The default value is 2GB. If MyISAM index files exceed this size and
	  disk space is available, increasing the value may help performance.

       ·  myisam_recover_options

	  The value of the --myisam-recover option. See the section called
	  “COMMAND OPTIONS”. This variable was added in MySQL 3.23.36.

       ·  myisam_repair_threads

	  If this value is greater than 1, MyISAM table indexes are created in
	  parallel (each index in its own thread) during the Repair by sorting
	  process. The default value is 1.

	  Note: Multi-threaded repair is still beta-quality code. This
	  variable was added in MySQL 4.0.13.

       ·  myisam_sort_buffer_size

	  The size of the buffer that is allocated when sorting MyISAM indexes
	  during a REPAIR TABLE or when creating indexes with CREATE INDEX or
	  ALTER TABLE. This variable was added in MySQL 3.23.16.

       ·  myisam_stats_method

	  How the server treats NULL values when collecting statistics about
	  the distribution of index values for MyISAM tables. This variable
	  has two possible values, nulls_equal and nulls_unequal. For
	  nulls_equal, all NULL index values are considered equal and form a
	  single value group that has a size equal to the number of NULL
	  values. For nulls_unequal, NULL values are considered unequal, and
	  each NULL forms a distinct value group of size 1.

	  The method that is used for generating table statistics influences
	  how the optimizer chooses indexes for query execution, as described
	  in Section 4.7, “MyISAM Index Statistics Collection”.

	  This variable was added in MySQL 4.1.15/5.0.14. For older versions,
	  the statistics collection method is equivalent to nulls_equal.

       ·  named_pipe

	  On Windows, indicates whether the server supports connections over
	  named pipes. This variable was added in MySQL 3.23.50.

       ·  ndb_autoincrement_prefetch_sz

	  Determines the probability of gaps in an autoincremented column. Set
	  to 1 to minimize this. Set to a high value for optimization — makes
	  inserts faster, but decreases the likelihood that consecutive
	  autoincrement numbers will be used in a batch of inserts. Default
	  value: 32. Mimimum value: 1.

       ·  ndb_cache_check_time

	  The number of milliseconds to wait before checking the NDB query
	  cache. Setting this to 0 (the default and minimum value) means that
	  the NDB query cache will be checked for validation on every query.

	  The recommended maximum value for this variable is 1000, which means
	  that the query cache is checked once per second. A larger value
	  means the NDB query cache is less often checked and invalidated due
	  to updates on a different mysqld. It is generally not desirable to
	  set this to a value greater than 2000.

       ·  ndb_force_send

	  Forces sending of buffers to NDB immediately, without waiting for
	  other threads. Defaults to ON.

       ·  ndb_index_stat_cache_entries

	  Sets the granularity of the statistics by determining the number of
	  starting and ending keys to store in the statistics memory cache.
	  Zero means no caching takes place; in this case, the data nodes are
	  always queries directly. Default value: 32.

       ·  ndb_index_stat_enable

	  Use NDB index statistics in query optimization. Defaults to ON.

       ·  ndb_index_stat_update_freq

	  How often to query data nodes instead of the statistics cache. For
	  example, a value of 20 (the default) means to direct every 20th
	  query to the data nodes.

       ·  ndb_report_thresh_binlog_epoch_slip

	  This is a threshold on the number of epochs to be behind before
	  reporting binlog status. For example, a value of 3 (the default)
	  means that if the difference between which epoch has been received
	  from the storage nodes and which epoch has been applied to the
	  binlog is 3 or more, a status message will be sent to the cluster
	  log.

       ·  ndb_report_thresh_binlog_mem_usage

	  This is a threshold on the percentage of free memory remaining
	  before reporting binlog status. For example, a value of 10 (the
	  default) means that if the amount of available memory for receiving
	  binlog data from the data nodes falls below 10%, a status message
	  will be sent to the cluster log.

       ·  ndb_use_exact_count

	  Forces NDB to use a count of records during SELECT COUNT(*) query
	  planning to speed up this type of query. The default value is ON.
	  For faster queries overall, disable this feature by setting the
	  value of ndb_use_exact_count to OFF.

       ·  ndb_use_transactions

	  You can disable NDB transaction support by setting this variable's
	  values to OFF (not recommended). The default is ON.

       ·  net_buffer_length

	  Each client thread is associated with a connection buffer and result
	  buffer. Both begin with a size given by net_buffer_length but are
	  dynamically enlarged up to max_allowed_packet bytes as needed. The
	  result buffer shrinks to net_buffer_length after each SQL statement.

	  This variable should not normally be changed, but if you have very
	  little memory, you can set it to the expected length of statements
	  sent by clients. If statements exceed this length, the connection
	  buffer is automatically enlarged.

       ·  net_read_timeout

	  The number of seconds to wait for more data from a connection before
	  aborting the read. This timeout applies only to TCP/IP connections,
	  not to connections made via Unix socket files, named pipes, or
	  shared memory. When the server is reading from the client,
	  net_read_timeout is the timeout value controlling when to abort.
	  When the server is writing to the client, net_write_timeout is the
	  timeout value controlling when to abort. See also slave_net_timeout.
	  This variable was added in MySQL 3.23.20.

       ·  net_retry_count

	  If a read on a communication port is interrupted, retry this many
	  times before giving up. This value should be set quite high on
	  FreeBSD because internal interrupts are sent to all threads. This
	  variable was added in MySQL 3.23.7.

       ·  net_write_timeout

	  The number of seconds to wait for a block to be written to a
	  connection before aborting the write. This timeout applies only to
	  TCP/IP connections, not to connections made via Unix socket files,
	  named pipes, or shared memory. See also net_read_timeout. This
	  variable was added in MySQL 3.23.20.

       ·  new

	  This variable is used in MySQL 4.0 to turn on some 4.1 behaviors.
	  This variable was added in MySQL 4.0.12.

       ·  old_passwords

	  Whether the server should use pre-4.1-style passwords for MySQL user
	  accounts. This variable was added in MySQL 4.1.1.

       ·  one_shot

	  This is not a variable, but it can be used when setting some
	  variables. It is described in Section 5.3, “SET Syntax”.

       ·  open_files_limit

	  The number of files that the operating system allows mysqld to open.
	  This is the real value allowed by the system and might be different
	  from the value you gave using the --open-files-limit option to
	  mysqld or mysqld_safe. The value is 0 on systems where MySQL can't
	  change the number of open files. This variable was added in MySQL
	  3.23.20.

       ·  pid_file

	  The pathname of the process ID (PID) file. This variable can be set
	  with the --pid-file option. This variable was added in MySQL
	  3.23.23.

       ·  port

	  The number of the port on which the server listens for TCP/IP
	  connections. This variable can be set with the --port option.

       ·  preload_buffer_size

	  The size of the buffer that is allocated when preloading indexes.
	  This variable was added in MySQL 4.1.1.

       ·  prepared_stmt_count

	  The current number of prepared statements. (The maximum number of
	  statements is given by the max_prepared_stmt_count system variable.)
	  This variable was added in MySQL 4.1.19.

       ·  protocol_version

	  The version of the client/server protocol used by the MySQL server.
	  This variable was added in MySQL 3.23.18.

       ·  query_alloc_block_size

	  The allocation size of memory blocks that are allocated for objects
	  created during statement parsing and execution. If you have problems
	  with memory fragmentation, it might help to increase this a bit.
	  This variable was added in MySQL 4.0.16.

       ·  query_cache_limit

	  Don't cache results that are larger than this number of bytes. The
	  default value is 1MB. This variable was added in MySQL 4.0.1.

       ·  query_cache_min_res_unit

	  The minimum size for blocks allocated by the query cache. The
	  default value is 4KB. Tuning information for this variable is given
	  in Section 12.3, “Query Cache Configuration”. This variable is
	  present from MySQL 4.1.

       ·  query_cache_size

	  The amount of memory allocated for caching query results. The
	  default value is 0, which disables the query cache. The allowable
	  values are multiples of 1024; other values are rounded down to the
	  nearest multiple. Note that query_cache_size bytes of memory are
	  allocated even if query_cache_type is set to 0. This variable was
	  added in MySQL 4.0.1.

       ·  query_cache_type

	  Set the query cache type. Setting the GLOBAL value sets the type for
	  all clients that connect thereafter. Individual clients can set the
	  SESSION value to affect their own use of the query cache.

	  ┌────────────┬────────────────────────────────────────┐
	  │Option      │ Description				│
	  ├────────────┼────────────────────────────────────────┤
	  │0 or OFF    │ Don't cache results in or		│
	  │	       │ retrieve results from the		│
	  │	       │ query cache. Note			│
	  │	       │		       that		│
	  │	       │ this does not deallocate		│
	  │	       │ the query cache			│
	  │	       │		       buffer.		│
	  │	       │ To do that, you should set		│
	  │	       │		       query_cache_size │
	  │	       │ to					│
	  │	       │		       0.		│
	  ├────────────┼────────────────────────────────────────┤
	  │1 or ON     │ Cache all query results except for	│
	  │	       │ those that begin with SELECT		│
	  │	       │		       SQL_NO_CACHE.	│
	  ├────────────┼────────────────────────────────────────┤
	  │2 or DEMAND │ Cache results only for queries that	│
	  │	       │ begin with SELECT			│
	  │	       │		       SQL_CACHE.	│
	  └────────────┴────────────────────────────────────────┘
	  This variable was added in MySQL 4.0.3.

       ·  query_cache_wlock_invalidate

	  Normally, when one client acquires a WRITE lock on a MyISAM table,
	  other clients are not blocked from issuing statements that read from
	  the table if the query results are present in the query cache.
	  Setting this variable to 1 causes acquisition of a WRITE lock for a
	  table to invalidate any queries in the query cache that refer to the
	  table. This forces other clients that attempt to access the table to
	  wait while the lock is in effect. This variable was added in MySQL
	  4.0.19.

       ·  query_prealloc_size

	  The size of the persistent buffer used for statement parsing and
	  execution. This buffer is not freed between statements. If you are
	  running complex queries, a larger query_prealloc_size value might be
	  helpful in improving performance, because it can reduce the need for
	  the server to perform memory allocation during query execution
	  operations.

	  This variable was added in MySQL 4.0.16.

       ·  range_alloc_block_size

	  The size of blocks that are allocated when doing range optimization.
	  This variable was added in MySQL 4.0.16.

       ·  read_buffer_size

	  Each thread that does a sequential scan allocates a buffer of this
	  size for each table it scans. If you do many sequential scans, you
	  might want to increase this value. This variable was added in MySQL
	  4.0.3. Previously, it was named record_buffer.

       ·  read_only

	  When the variable is set to ON for a replication slave server, it
	  causes the slave to allow no updates except from slave threads or
	  from users that have the SUPER privilege. This can be useful to
	  ensure that a slave server accepts updates only from its master
	  server and not from clients. This variable was added in MySQL
	  4.0.14.

       ·  read_rnd_buffer_size

	  When reading rows in sorted order following a key-sorting operation,
	  the rows are read through this buffer to avoid disk seeks. Setting
	  the variable to a large value can improve ORDER BY performance by a
	  lot. However, this is a buffer allocated for each client, so you
	  should not set the global variable to a large value. Instead, change
	  the session variable only from within those clients that need to run
	  large queries. This variable was added in MySQL 4.0.3. Previously,
	  it was named record_rnd_buffer.

       ·  relay_log_purge

	  Disables or enables automatic purging of relay logs as soon as they
	  are not needed any more. The default value is 1 (ON). This variable
	  was added in MySQL 4.1.1.

       ·  safe_show_database

	  Do not show databases for which the user has no database or table
	  privileges. This can improve security if you are concerned about
	  people being able to see what databases other users have. See also
	  skip_show_database.

	  This variable was removed in MySQL 4.0.5. Beginning with this
	  version, you should instead use the SHOW DATABASES privilege to
	  control access by MySQL accounts to databases.

       ·  rpl_recovery_rank

	  This variable is unused.

       ·  secure_auth

	  If the MySQL server has been started with the --secure-auth option,
	  it blocks connections from all accounts that have passwords stored
	  in the old (pre-4.1) format. In that case, the value of this
	  variable is ON, otherwise it is OFF.

	  You should enable this option if you want to prevent all use of
	  passwords in the old format (and hence insecure communication over
	  the network). This variable was added in MySQL 4.1.1.

	  Server startup fails with an error if this option is enabled and the
	  privilege tables are in pre-4.1 format.

       ·  server_id

	  The server ID. This value is set by the --server-id option. It is
	  used for replication to enable master and slave servers to identify
	  themselves uniquely. This variable was added in MySQL 3.23.26.

       ·  shared_memory

	  (Windows only.) Whether the server allows shared-memory connections.
	  This variable was added in MySQL 4.1.1.

       ·  shared_memory_base_name

	  (Windows only.) The name of shared memory to use for shared-memory
	  connections. This is useful when running multiple MySQL instances on
	  a single physical machine. This variable was added in MySQL 4.1.0.

       ·  skip_external_locking

	  This is OFF if mysqld uses external locking, ON if external locking
	  is disabled. This variable was added in MySQL 4.0.3. Previously, it
	  was named skip_locking.

       ·  skip_networking

	  This is ON if the server allows only local (non-TCP/IP) connections.
	  On Unix, local connections use a Unix socket file. On Windows, local
	  connections use a named pipe or shared memory. On NetWare, only
	  TCP/IP connections are supported, so do not set this variable to ON.
	  This variable can be set to ON with the --skip-networking option.
	  This variable was added in MySQL 3.22.23.

       ·  skip_show_database

	  This prevents people from using the SHOW DATABASES statement if they
	  do not have the SHOW DATABASES privilege. This can improve security
	  if you are concerned about people being able to see what databases
	  other users have. See also safe_show_database. This variable was
	  added in MySQL 3.23.4. As of MySQL 4.0.2, its effect also depends on
	  the SHOW DATABASES privilege: If the variable value is ON, the SHOW
	  DATABASES statement is allowed only to users who have the SHOW
	  DATABASES privilege, and the statement displays all database names.
	  If the value is OFF, SHOW DATABASES is allowed to all users, but
	  displays each database name only if the user has the SHOW DATABASES
	  privilege or some privilege for the database. Note that any global
	  privilege is a privilege for the database.

       ·  slave_compressed_protocol

	  Whether to use compression of the master/slave protocol if both the
	  slave and the master support it. This variable was added in MySQL
	  4.0.3.

       ·  slave_load_tmpdir

	  The name of the directory where the slave creates temporary files
	  for replicating LOAD DATA INFILE statements. This variable was added
	  in MySQL 4.0.0.

       ·  slave_net_timeout

	  The number of seconds to wait for more data from a master/slave
	  connection before aborting the read. This timeout applies only to
	  TCP/IP connections, not to connections made via Unix socket files,
	  named pipes, or shared memory. This variable was added in MySQL
	  3.23.40.

       ·  slave_skip_errors

	  The replication errors that the slave should skip (ignore). This
	  variable was added in MySQL 3.23.47.

       ·  slave_transaction_retries

	  If a replication slave SQL thread fails to execute a transaction
	  because of an InnoDB deadlock or InnoDB's innodb_lock_wait_timeout
	  or NDB Cluster's TransactionDeadlockDetectionTimeout or
	  TransactionInactiveTimeout was exceeded, it automatically retries
	  slave_transaction_retries times before stopping with an error. The
	  default in MySQL 4.1 is 0. You must explicitly set the value to
	  greater than 0 to enable the “retry” behavior, which is probably a
	  good idea.

       ·  slow_launch_time

	  If creating a thread takes longer than this many seconds, the server
	  increments the Slow_launch_threads status variable. This variable
	  was added in MySQL 3.23.15.

       ·  socket

	  On Unix platforms, this variable is the name of the socket file that
	  is used for local client connections. The default is
	  /tmp/mysql.sock. (For some distribution formats, the directory might
	  be different, such as /var/lib/mysql for RPMs.)

	  On Windows, this variable is the name of the named pipe that is used
	  for local client connections. The default value is MySQL (not case
	  sensitive).

       ·  sort_buffer_size

	  Each thread that needs to do a sort allocates a buffer of this size.
	  Increase this value for faster ORDER BY or GROUP BY operations. See
	  Section 4.4, “Where MySQL Stores Temporary Files”.

       ·  sql_mode

	  The current server SQL mode. This variable was added in MySQL
	  3.23.41. It can be set dynamically as of MySQL 4.1.1. See the
	  section called “SQL MODES”.

       ·  sql_slave_skip_counter

	  The number of events from the master that a slave server should
	  skip. See Section 6.2.6, “SET GLOBAL SQL_SLAVE_SKIP_COUNTER Syntax”.
	  This variable was added in MySQL 3.23.33.

       ·  storage_engine

	  This variable is a synonym for table_type. It was added in MySQL
	  4.1.2.

       ·  sync_binlog

	  If the value of this variable is positive, the MySQL server
	  synchronizes its binary log to disk (using fdatasync()) after every
	  sync_binlog writes to the binary log. Note that there is one write
	  to the binary log per statement if autocommit is enabled, and one
	  write per transaction otherwise. The default value is 0, which does
	  no synchronizing to disk. A value of 1 is the safest choice, because
	  in the event of a crash you lose at most one statement or
	  transaction from the binary log. However, it is also the slowest
	  choice (unless the disk has a battery-backed cache, which makes
	  synchronization very fast). This variable was added in MySQL 4.1.3.

	  If the value of sync_binlog is 0 (the default), no extra flushing is
	  done. The server relies on the operating system to flush the file
	  contents occasionaly as for any other file.

       ·  sync_frm

	  If this variable is set to 1, when any non-temporary table is
	  created its .frm file is synchronized to disk (using fdatasync()).
	  This is slower but safer in case of a crash. The default is 1. This
	  was added as a command-line option in MySQL 4.0.18. It is also a
	  settable global variable as of MySQL 4.1.3.

       ·  system_time_zone

	  The server system time zone. When the server begins executing, it
	  inherits a time zone setting from the machine defaults, possibly
	  modified by the environment of the account used for running the
	  server or the startup script. The value is used to set
	  system_time_zone. Typically the time zone is specified by the TZ
	  environment variable. It also can be specified using the --timezone
	  option of the mysqld_safe script. This variable was added in MySQL
	  4.1.3.

       ·  table_cache

	  The number of open tables for all threads. Increasing this value
	  increases the number of file descriptors that mysqld requires. You
	  can check whether you need to increase the table cache by checking
	  the Opened_tables status variable. See the section called “STATUS
	  VARIABLES”. If the value of Opened_tables is large and you do not do
	  FLUSH TABLES often (which just forces all tables to be closed and
	  reopened), then you should increase the value of the table_cache
	  variable. For more information about the table cache, see
	  Section 4.8, “How MySQL Opens and Closes Tables”.

       ·  table_type

	  The default table type (storage engine). To set the table type at
	  server startup, use the --default-table-type option. This variable
	  was added in MySQL 3.23.0. See the section called “COMMAND OPTIONS”.

       ·  thread_cache_size

	  How many threads the server should cache for reuse. When a client
	  disconnects, the client's threads are put in the cache if there are
	  fewer than thread_cache_size threads there. Requests for threads are
	  satisfied by reusing threads taken from the cache if possible, and
	  only when the cache is empty is a new thread created. This variable
	  can be increased to improve performance if you have a lot of new
	  connections. (Normally, this doesn't provide a notable performance
	  improvement if you have a good thread implementation.) By examining
	  the difference between the Connections and Threads_created status
	  variables, you can see how efficient the thread cache is. For
	  details, see the section called “STATUS VARIABLES”. This variable
	  was added in MySQL 3.23.16.

       ·  thread_concurrency

	  On Solaris, mysqld calls thr_setconcurrency() with this value. This
	  function enables applications to give the threads system a hint
	  about the desired number of threads that should be run at the same
	  time. This variable was added in MySQL 3.23.7.

       ·  thread_stack

	  The stack size for each thread. Many of the limits detected by the
	  crash-me test are dependent on this value. The default is large
	  enough for normal operation. See Section 1.4, “The MySQL Benchmark
	  Suite”. The default is 64KB before MySQL 4.0.10 and 192KB
	  thereafter.

       ·  time_format

	  This variable is not implemented.

       ·  time_zone

	  The current time zone. This variable is used to initialize the time
	  zone for each client that connects. By default, the initial value of
	  this is ´SYSTEM' (which means, “use the value of system_time_zone”).
	  The value can be specified explicitly at server startup with the
	  --default-time-zone option. See Section 9.8, “MySQL Server Time Zone
	  Support”. This variable was added in MySQL 4.1.3.

       ·  timezone

	  The time zone for the server. This is set from the TZ environment
	  variable when mysqld is started. The time zone also can be set by
	  giving a --timezone argument to mysqld_safe. This variable was added
	  in MySQL 3.23.15. As of MySQL 4.1.3, it is obsolete and has been
	  replaced by the system_time_zone variable. See Section 4.6, “Time
	  Zone Problems”.

       ·  tmp_table_size

	  The maximum size of in-memory temporary tables. (The actual limit is
	  determined as the smaller of max_heap_table_size and
	  tmp_table_size.) If an in-memory temporary table exceeds the limit,
	  MySQL automatically converts it to an on-disk MyISAM table. Increase
	  the value of tmp_table_size (and max_heap_table_size if necessary)
	  if you do many advanced GROUP BY queries and you have lots of
	  memory.

       ·  tmpdir

	  The directory used for temporary files and temporary tables.
	  Starting from MySQL 4.1, this variable can be set to a list of
	  several paths that are used in round-robin fashion. Paths should be
	  separated by colon characters (‘:’) on Unix and semicolon characters
	  (‘;’) on Windows, NetWare, and OS/2.

	  The multiple-directory feature can be used to spread the load
	  between several physical disks. If the MySQL server is acting as a
	  replication slave, you should not set tmpdir to point to a directory
	  on a memory-based filesystem or to a directory that is cleared when
	  the server host restarts. A replication slave needs some of its
	  temporary files to survive a machine restart so that it can
	  replicate temporary tables or LOAD DATA INFILE operations. If files
	  in the temporary file directory are lost when the server restarts,
	  replication fails. However, if you are using MySQL 4.0.0 or later,
	  you can set the slave's temporary directory using the
	  slave_load_tmpdir variable. In that case, the slave won't use the
	  general tmpdir value and you can set tmpdir to a non-permanent
	  location.

	  This variable was added in MySQL 3.22.4.

       ·  transaction_alloc_block_size

	  The amount in bytes by which to increase a per-transaction memory
	  pool which needs memory. See the description of
	  transaction_prealloc_size. This variable was added in MySQL 4.0.16.

       ·  transaction_prealloc_size

	  There is a per-transaction memory pool from which various
	  transaction-related allocations take memory. The initial size of the
	  pool in bytes is transaction_prealloc_size. For every allocation
	  that cannot be satisfied from the pool because it has insufficient
	  memory available, the pool is increased by
	  transaction_alloc_block_size bytes. When the transaction ends, the
	  pool is truncated to transaction_prealloc_size bytes.

	  By making transaction_prealloc_size sufficiently large to contain
	  all statements within a single transaction, you can avoid many
	  malloc() calls. This variable was added in MySQL 4.0.16.

	  The system_time_zone variable differs from time_zone. Although they
	  might have the same value, the latter variable is used to initialize
	  the time zone for each client that connects. See Section 9.8, “MySQL
	  Server Time Zone Support”.

       ·  tx_isolation

	  The default transaction isolation level. This variable was added in
	  MySQL 4.0.3.

	  This variable is set by the SET TRANSACTION ISOLATION LEVEL
	  statement. See Section 4.6, “SET TRANSACTION Syntax”. If you set
	  tx_isolation directly to an isolation level name that contains a
	  space, the name should be enclosed within quotes, with the space
	  replaced by a dash. For example:

	  SET tx_isolation = 'READ-COMMITTED';

       ·  version

	  The version number for the server.

       ·  version_bdb

	  The BDB storage engine version. This variable was added in MySQL
	  3.23.31 with the name bdb_version and renamed to version_bdb in
	  MySQL 4.1.1.

       ·  version_comment

	  The configure script has a --with-comment option that allows a
	  comment to be specified when building MySQL. This variable contains
	  the value of that comment. This variable was added in MySQL 4.0.17.

       ·  version_compile_machine

	  The type of machine or architecture on which MySQL was built. This
	  variable was added in MySQL 4.1.1.

       ·  version_compile_os

	  The type of operating system on which MySQL was built. This variable
	  was added in MySQL 4.0.19.

       ·  wait_timeout

	  The number of seconds the server waits for activity on a
	  non-interactive connection before closing it. This timeout applies
	  only to TCP/IP connections, not to connections made via Unix socket
	  files, named pipes, or shared memory.

	  On thread startup, the session wait_timeout value is initialized
	  from the global wait_timeout value or from the global
	  interactive_timeout value, depending on the type of client (as
	  defined by the CLIENT_INTERACTIVE connect option to
	  mysql_real_connect()). See also interactive_timeout.

USING SYSTEM VARIABLES
       The mysql server maintains many system variables that indicate how it
       is configured.  the section called “SYSTEM VARIABLES”, describes the
       meaning of these variables. Each system variable has a default value.
       System variables can be set at server startup using options on the
       command line or in an option file. As of MySQL 4.0.3, most of them can
       be changed dynamically while the server is running by means of the SET
       statement, which enables you to modify operation of the server without
       having to stop and restart it. You can refer to system variable values
       in expressions.

       Beginning with MySQL 4.0.3, the server maintains two kinds of system
       variables. Global variables affect the overall operation of the server.
       Session variables affect its operation for individual client
       connections. A given system variable can have both a global and a
       session value. Global and session system variables are related as
       follows:

       ·  When the server starts, it initializes all global variables to their
	  default values. These defaults can be changed by options specified
	  on the command line or in an option file. (See Section 3,
	  “Specifying Program Options”.)

       ·  The server also maintains a set of session variables for each client
	  that connects. The client's session variables are initialized at
	  connect time using the current values of the corresponding global
	  variables. For example, the client's SQL mode is controlled by the
	  session sql_mode value, which is initialized when the client
	  connects to the value of the global sql_mode value.

       System variable values can be set globally at server startup by using
       options on the command line or in an option file. When you use a
       startup option to set a variable that takes a numeric value, the value
       can be given with a suffix of K, M, or G (either uppercase or
       lowercase) to indicate a multiplier of 1024, 10242 or 10243; that is,
       units of kilobytes, megabytes, or gigabytes, respectively. Thus, the
       following command starts the server with a query cache size of 16
       megabytes and a maximum packet size of one gigabyte:

	  mysqld --query_cache_size=16M --max_allowed_packet=1G

       Before MySQL 4.0.2, use this syntax instead:

	  mysqld --set-variable=query_cache_size=16M \
		 --set-variable=max_allowed_packet=1G

       Within an option file, those variables are set like this:

	  [mysqld]
	  query_cache_size=16M
	  max_allowed_packet=1G

       Or like this before MySQL 4.0.2:

	  [mysqld]
	  set-variable=query_cache_size=16M
	  set-variable=max_allowed_packet=1G

       The lettercase of suffix letters does not matter; 16M and 16m are
       equivalent, as are 1G and 1g.

       If you want to restrict the maximum value to which a system variable
       can be set at runtime with the SET statement, you can specify this
       maximum by using an option of the form --maximum-var_name=value at
       server startup. For example, to prevent the value of query_cache_size
       from being increased to more than 32MB at runtime, use the option
       --maximum-query_cache_size=32M. This feature is available as of MySQL
       4.0.2.

       Many system variables are dynamic and can be changed while the server
       runs by using the SET statement. For a list, see the section called
       “Dynamic System Variables”. To change a system variable with SET, refer
       to it as var_name, optionally preceded by a modifier:

       ·  To indicate explicitly that a variable is a global variable, precede
	  its name by GLOBAL or @@global.. The SUPER privilege is required to
	  set global variables.

       ·  To indicate explicitly that a variable is a session variable,
	  precede its name by SESSION, @@session., or @@. Setting a session
	  variable requires no special privilege, but a client can change only
	  its own session variables, not those of any other client.

       ·  LOCAL and @@local.  are synonyms for SESSION and @@session..

       ·  If no modifier is present, SET changes the session variable.

       A SET statement can contain multiple variable assignments, separated by
       commas. If you set several system variables, the most recent GLOBAL or
       SESSION modifier in the statement is used for following variables that
       have no modifier specified.

       Examples:

	  SET sort_buffer_size=10000;
	  SET @@local.sort_buffer_size=10000;
	  SET GLOBAL sort_buffer_size=1000000, SESSION sort_buffer_size=1000000;
	  SET @@sort_buffer_size=1000000;
	  SET @@global.sort_buffer_size=1000000, @@local.sort_buffer_size=1000000;

       When you assign a value to a system variable with SET, you cannot use
       suffix letters in the value (as can be done with startup options).
       However, the value can take the form of an expression:

	  SET sort_buffer_size = 10 * 1024 * 1024;

       The @@var_name syntax for system variables is supported for
       compatibility with some other database systems.

       If you change a session system variable, the value remains in effect
       until your session ends or until you change the variable to a different
       value. The change is not visible to other clients.

       If you change a global system variable, the value is remembered and
       used for new connections until the server restarts. (To make a global
       system variable setting permanent, you should set it in an option
       file.) The change is visible to any client that accesses that global
       variable. However, the change affects the corresponding session
       variable only for clients that connect after the change. The global
       variable change does not affect the session variable for any client
       that is currently connected (not even that of the client that issues
       the SET GLOBAL statement).

       To prevent incorrect usage, MySQL produces an error if you use SET
       GLOBAL with a variable that can only be used with SET SESSION or if you
       do not specify GLOBAL (or @@global.) when setting a global variable.

       To set a SESSION variable to the GLOBAL value or a GLOBAL value to the
       compiled-in MySQL default value, use the DEFAULT keyword. For example,
       the following two statements are identical in setting the session value
       of max_join_size to the global value:

	  SET max_join_size=DEFAULT;
	  SET @@session.max_join_size=@@global.max_join_size;

       Not all system variables can be set to DEFAULT. In such cases, use of
       DEFAULT results in an error.

       You can refer to the values of specific global or sesson system
       variables in expressions by using one of the @@-modifiers. For example,
       you can retrieve values in a SELECT statement like this:

	  SELECT @@global.sql_mode, @@session.sql_mode, @@sql_mode;

       When you refer to a system variable in an expression as @@var_name
       (that is, when you do not specify @@global.  or @@session.), MySQL
       returns the session value if it exists and the global value otherwise.
       (This differs from SET @@var_name = value, which always refers to the
       session value.)

       Note: Some system variables can be enabled with the SET statement by
       setting them to ON or 1, or disabled by setting them to OFF or 0.
       However, to set such a variable on the command line or in an option
       file, you must set it to 1 or 0; setting it to ON or OFF will not work.
       For example, on the command line, --delay_key_write=1 works but
       --delay_key_write=ON does not.

       To display system variable names and values, use the SHOW VARIABLES
       statement:

	  mysql> SHOW VARIABLES;
	  +---------------------------------+-------------------------------------+
	  | Variable_name		    | Value				  |
	  +---------------------------------+-------------------------------------+
	  | back_log			    | 50				  |
	  | basedir			    | /usr/local/mysql			  |
	  | bdb_cache_size		    | 8388600				  |
	  | bdb_home			    | /usr/local/mysql			  |
	  | bdb_log_buffer_size		    | 32768				  |
	  | bdb_logdir			    |					  |
	  | bdb_max_lock		    | 10000				  |
	  | bdb_shared_data		    | OFF				  |
	  | bdb_tmpdir			    | /tmp/				  |
	  | binlog_cache_size		    | 32768				  |
	  | bulk_insert_buffer_size	    | 8388608				  |
	  | character_set_client	    | latin1				  |
	  | character_set_connection	    | latin1				  |
	  | character_set_database	    | latin1				  |
	  | character_set_results	    | latin1				  |
	  | character_set_server	    | latin1				  |
	  | character_set_system	    | utf8				  |
	  | character_sets_dir		    | /usr/local/mysql/share/charsets/	  |
	  | collation_connection	    | latin1_swedish_ci			  |
	  | collation_database		    | latin1_swedish_ci			  |
	  | collation_server		    | latin1_swedish_ci			  |
	  | innodb_additional_mem_pool_size | 1048576				  |
	  | innodb_autoextend_increment	    | 8					  |
	  | innodb_buffer_pool_awe_mem_mb   | 0					  |
	  | innodb_buffer_pool_size	    | 8388608				  |
	  | innodb_data_file_path	    | ibdata1:10M:autoextend		  |
	  | innodb_data_home_dir	    |					  |
	  | version			    | 4.1.18-max-log			  |
	  | version_comment		    | MySQL Community Edition - Max (GPL) |
	  | version_compile_machine	    | i686				  |
	  | version_compile_os		    | pc-linux-gnu			  |
	  | wait_timeout		    | 28800				  |
	  +---------------------------------+-------------------------------------+

       With a LIKE clause, the statement displays only those variables that
       match the pattern. To obtain a specific variable name, use a LIKE
       clause as shown:

	  SHOW VARIABLES LIKE 'max_join_size';
	  SHOW SESSION VARIABLES LIKE 'max_join_size';

       To get a list of variables whose name match a pattern, use the ‘%’
       wildcard character in a LIKE clause:

	  SHOW VARIABLES LIKE '%size%';
	  SHOW GLOBAL VARIABLES LIKE '%size%';

       Wildcard characters can be used in any position within the pattern to
       be matched. Strictly speaking, because ‘_’ is a wildcard that matches
       any single character, you should escape it as ‘\_’ to match it
       literally. In practice, this is rarely necessary.

       For SHOW VARIABLES, if you specify neither GLOBAL nor SESSION, MySQL
       returns SESSION values.

       The reason for requiring the GLOBAL keyword when setting GLOBAL-only
       variables but not when retrieving them is to prevent problems in the
       future. If we were to remove a SESSION variable that has the same name
       as a GLOBAL variable, a client with the SUPER privilege might
       accidentally change the GLOBAL variable rather than just the SESSION
       variable for its own connection. If we add a SESSION variable with the
       same name as a GLOBAL variable, a client that intends to change the
       GLOBAL variable might find only its own SESSION variable changed.

   Structured System Variables
       Structured system variables are supported beginning with MySQL 4.1.1. A
       structured variable differs from a regular system variable in two
       respects:

       ·  Its value is a structure with components that specify server
	  parameters considered to be closely related.

       ·  There might be several instances of a given type of structured
	  variable. Each one has a different name and refers to a different
	  resource maintained by the server.

       In MySQL 4.1 (4.1.1 and above), MySQL supports one structured variable
       type. It specifies parameters that govern the operation of key caches.
       A key cache structured variable has these components:

       ·  key_buffer_size

       ·  key_cache_block_size

       ·  key_cache_division_limit

       ·  key_cache_age_threshold

       The purpose of this section is to describe the syntax for referring to
       structured variables. Key cache variables are used for syntax examples,
       but specific details about how key caches operate are found elsewhere,
       in Section 4.6, “The MyISAM Key Cache”.

       To refer to a component of a structured variable instance, you can use
       a compound name in instance_name.component_name format. Examples:

	  hot_cache.key_buffer_size
	  hot_cache.key_cache_block_size
	  cold_cache.key_cache_block_size

       For each structured system variable, an instance with the name of
       default is always predefined. If you refer to a component of a
       structured variable without any instance name, the default instance is
       used. Thus, default.key_buffer_size and key_buffer_size both refer to
       the same system variable.

       Structured variable instances and components follow these naming rules:

       ·  For a given type of structured variable, each instance must have a
	  name that is unique within variables of that type. However, instance
	  names need not be unique across structured variable types. For
	  example, each structured variable has an instance named default, so
	  default is not unique across variable types.

       ·  The names of the components of each structured variable type must be
	  unique across all system variable names. If this were not true (that
	  is, if two different types of structured variables could share
	  component member names), it would not be clear which default
	  structured variable to use for references to member names that are
	  not qualified by an instance name.

       ·  If a structured variable instance name is not legal as an unquoted
	  identifier, refer to it as a quoted identifier using backticks. For
	  example, hot-cache is not legal, but `hot-cache` is.

       ·  global, session, and local are not legal instance names. This avoids
	  a conflict with notation such as @@global.var_name for referring to
	  non-structured system variables.

       At the moment, the first two rules have no possibility of being
       violated because the only structured variable type is the one for key
       caches. These rules will assume greater significance if some other type
       of structured variable is created in the future.

       With one exception, it is allowable to refer to structured variable
       components using compound names in any context where simple variable
       names can occur. For example, you can assign a value to a structured
       variable using a command-line option:

	  shell> mysqld --hot_cache.key_buffer_size=64K

       In an option file, use this syntax:

	  [mysqld]
	  hot_cache.key_buffer_size=64K

       If you start the server with such an option, it creates a key cache
       named hot_cache with a size of 64KB in addition to the default key
       cache that has a default size of 8MB.

       Suppose that you start the server as follows:

	  shell> mysqld --key_buffer_size=256K \
		   --extra_cache.key_buffer_size=128K \
		   --extra_cache.key_cache_block_size=2048

       In this case, the server sets the size of the default key cache to
       256KB. (You could also have written --default.key_buffer_size=256K.) In
       addition, the server creates a second key cache named extra_cache that
       has a size of 128KB, with the size of block buffers for caching table
       index blocks set to 2048 bytes.

       The following example starts the server with three different key caches
       having sizes in a 3:1:1 ratio:

	  shell> mysqld --key_buffer_size=6M \
		   --hot_cache.key_buffer_size=2M \
		   --cold_cache.key_buffer_size=2M

       Structured variable values may be set and retrieved at runtime as well.
       For example, to set a key cache named hot_cache to a size of 10MB, use
       either of these statements:

	  mysql> SET GLOBAL hot_cache.key_buffer_size = 10*1024*1024;
	  mysql> SET @@global.hot_cache.key_buffer_size = 10*1024*1024;

       To retrieve the cache size, do this:

	  mysql> SELECT @@global.hot_cache.key_buffer_size;

       However, the following statement does not work. The variable is not
       interpreted as a compound name, but as a simple string for a LIKE
       pattern-matching operation:

	  mysql> SHOW GLOBAL VARIABLES LIKE 'hot_cache.key_buffer_size';

       This is the exception to being able to use structured variable names
       anywhere a simple variable name may occur.

   Dynamic System Variables
       Beginning with MySQL 4.0.3, many server system variables are dynamic
       and can be set at runtime using SET GLOBAL or SET SESSION. You can also
       select their values using SELECT. See the section called “USING SYSTEM
       VARIABLES”.

       The following table shows the full list of all dynamic system
       variables. The last column indicates for each variable whether GLOBAL
       or SESSION (or both) apply. The table also lists session options that
       can be set with the SET statement.  Section 5.3, “SET Syntax”,
       discusses these options.

       Variables that have a type of “string” take a string value. Variables
       that have a type of “numeric” take a numeric value. Variables that have
       a type of “boolean” can be set to 0, 1, ON or OFF. (If you set them on
       the command line or in an option file, use the numeric values.)
       Variables that are marked as “enumeration” normally should be set to
       one of the available values for the variable, but can also be set to
       the number that corresponds to the desired enumeration value. For
       enumerated system variables, the first enumeration value corresponds to
       0. This differs from ENUM columns, for which the first enumeration
       value corresponds to 1.

       ┌─────────────────────────────┬────────────────┬──────────────────┐
       │Variable Name		     │ Value Type     │ Type		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │collation_connection	     │ string	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_log_update		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_low_priority_updates     │ boolean	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_max_join_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_mode		     │ enumeration    │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_notes		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_quote_show_create	     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_safe_updates	     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_select_limit	     │ numeric	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_slave_skip_counter	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │updatable_views_with_limit   │ enumeration    │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │collation_server	     │ string	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_warnings		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sync_binlog		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sync_frm		     │ boolean	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │storage_engine		     │ enumeration    │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │table_cache		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │table_type		     │ enumeration    │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │thread_cache_size	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │time_zone		     │ string	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │timestamp		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │tmp_table_size		     │ enumeration    │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │concurrent_insert	     │ boolean	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │transaction_alloc_block_size │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │transaction_prealloc_size    │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │tx_isolation		     │ enumeration    │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │unique_checks		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │wait_timeout		     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │warning_count		     │ numeric	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │connect_timeout		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │convert_character_set	     │ string	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │default_week_format	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │delay_key_write		     │ OFF | ON | ALL │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │delayed_insert_limit	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │delayed_insert_timeout	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │delayed_queue_size	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │autocommit		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │error_count		     │ numeric	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │expire_logs_days	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │flush			     │ boolean	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │flush_time		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │foreign_key_checks	     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │ft_boolean_syntax	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │group_concat_max_len	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │identity		     │ numeric	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │innodb_autoextend_increment  │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │innodb_concurrency_tickets   │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │big_tables		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │innodb_max_dirty_pages_pct   │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │innodb_max_purge_lag	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │innodb_sync_spin_loops	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │innodb_table_locks	     │ boolean	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │innodb_thread_sleep_delay    │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │insert_id		     │ numeric	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │interactive_timeout	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │join_buffer_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │key_buffer_size		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │last_insert_id		     │ numeric	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │binlog_cache_size	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │local_infile		     │ boolean	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │log_warnings		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │long_query_time		     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │low_priority_updates	     │ boolean	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_allowed_packet	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_binlog_cache_size	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_binlog_size		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_connect_errors	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_connections		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_delayed_threads	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │bulk_insert_buffer_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_error_count		     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_heap_table_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_insert_delayed_threads   │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_join_size		     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_prepared_stmt_count	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_relay_log_size	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_seeks_for_key	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_sort_length		     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_tmp_tables		     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_user_connections	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │character_set_client	     │ string	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │max_write_lock_count	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │multi_read_range	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │myisam_data_pointer_size     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │myisam_max_sort_file_size    │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │myisam_repair_threads	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │myisam_sort_buffer_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │myisam_stats_method	     │ enum	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │net_buffer_length	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │net_read_timeout	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │net_retry_count		     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │character_set_connection     │ string	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │net_write_timeout	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │old_passwords		     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │optimizer_prune_level	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │optimizer_search_depth	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │preload_buffer_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │query_alloc_block_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │query_cache_limit	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │query_cache_size	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │query_cache_type	     │ enumeration    │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │query_cache_wlock_invalidate │ boolean	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │character_set_results	     │ string	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │query_prealloc_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │range_alloc_block_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │read_buffer_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │read_only		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │read_rnd_buffer_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │rpl_recovery_rank	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │safe_show_database	     │ boolean	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │secure_auth		     │ boolean	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │server_id		     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │slave_compressed_protocol    │ boolean	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │character_set_server	     │ string	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │slave_net_timeout	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │slave_transaction_retries    │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │slow_launch_time	     │ numeric	      │ GLOBAL		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sort_buffer_size	     │ numeric	      │ GLOBAL | SESSION │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_auto_is_null	     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_big_selects		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_big_tables		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_buffer_result	     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_log_bin		     │ boolean	      │ SESSION		 │
       ├─────────────────────────────┼────────────────┼──────────────────┤
       │sql_log_off		     │ boolean	      │ SESSION		 │
       └─────────────────────────────┴────────────────┴──────────────────┘

STATUS VARIABLES
       The server maintains many status variables that provide information
       about its operation. You can view these variables and their values by
       using the SHOW STATUS statement:

	  mysql> SHOW STATUS;
	  +--------------------------+------------+
	  | Variable_name	     | Value	  |
	  +--------------------------+------------+
	  | Aborted_clients	     | 0	  |
	  | Aborted_connects	     | 0	  |
	  | Bytes_received	     | 155372598  |
	  | Bytes_sent		     | 1176560426 |
	  | Connections		     | 30023	  |

       Many status variables are reset to 0 by the FLUSH STATUS statement.

       The status variables have the following meanings. The Com_xxx statement
       counter variables were added beginning with MySQL 3.23.47. The
       Qcache_xxx query cache variables were added beginning with MySQL 4.0.1.
       Otherwise, variables with no version indicated have been present since
       at least MySQL 3.22.

       ·  Aborted_clients

	  The number of connections that were aborted because the client died
	  without closing the connection properly. See Section 2.10,
	  “Communication Errors and Aborted Connections”.

       ·  Aborted_connects

	  The number of failed attempts to connect to the MySQL server. See
	  Section 2.10, “Communication Errors and Aborted Connections”.

       ·  Binlog_cache_disk_use

	  The number of transactions that used the temporary binary log cache
	  but that exceeded the value of binlog_cache_size and used a
	  temporary file to store statements from the transaction. This
	  variable was added in MySQL 4.1.2.

       ·  Binlog_cache_use

	  The number of transactions that used the temporary binary log cache.
	  This variable was added in MySQL 4.1.2.

       ·  Bytes_received

	  The number of bytes received from all clients. This variable was
	  added in MySQL 3.23.7.

       ·  Bytes_sent

	  The number of bytes sent to all clients. This variable was added in
	  MySQL 3.23.7.

       ·  Com_xxx

	  The Com_xxx statement counter variables were added beginning with
	  MySQL 3.23.47. They indicate the number of times each xxx statement
	  has been executed. There is one status variable for each type of
	  statement. For example, Com_delete and Com_insert count DELETE and
	  INSERT statements, respectively. However, if a query result is
	  returned from query cache, the server increments the Qcache_hits
	  status variable, not Com_select. See Section 12.4, “Query Cache
	  Status and Maintenance”.

	  New Com_stmt_xxx status variables have been added in MySQL 4.1.13:

	  ·  Com_stmt_prepare

	  ·  Com_stmt_execute

	  ·  Com_stmt_send_long_data

	  ·  Com_stmt_reset

	  ·  Com_stmt_close

	  Those variables stand for prepared statement commands. Their names
	  refer to the COM_xxx command set used in the network layer. In other
	  words, their values increase whenever prepared statement API calls
	  such as mysql_stmt_prepare(), mysql_stmt_execute(), and so forth are
	  executed. However, Com_stmt_prepare, Com_stmt_execute and
	  Com_stmt_close also increase for PREPARE, EXECUTE, or DEALLOCATE
	  PREPARE, respectively. Additionally, the values of the older
	  (available since MySQL 4.1.3) statement counter variables
	  Com_prepare_sql, Com_execute_sql, and Com_dealloc_sql increase for
	  the PREPARE, EXECUTE, and DEALLOCATE PREPARE statements.

	  All of the Com_stmt_xxx variables are increased even if their
	  argument (a prepared statement) is unknown or an error occurred
	  during execution; in other words, their values correspond to the
	  number of requests issued, not to the number of requests
	  successfully completed.

       ·  Connections

	  The number of connection attempts (successful or not) to the MySQL
	  server.

       ·  Created_tmp_disk_tables

	  The number of temporary tables on disk created automatically by the
	  server while executing statements. This variable was added in MySQL
	  3.23.24.

       ·  Created_tmp_files

	  How many temporary files mysqld has created. This variable was added
	  in MySQL 3.23.28.

       ·  Created_tmp_tables

	  The number of in-memory temporary tables created automatically by
	  the server while executing statements. If Created_tmp_disk_tables is
	  large, you may want to increase the tmp_table_size value to cause
	  temporary tables to be memory-based instead of disk-based.

       ·  Delayed_errors

	  The number of rows written with INSERT DELAYED for which some error
	  occurred (probably duplicate key).

       ·  Delayed_insert_threads

	  The number of INSERT DELAYED handler threads in use.

       ·  Delayed_writes

	  The number of INSERT DELAYED rows written.

       ·  Flush_commands

	  The number of executed FLUSH statements.

       ·  Handler_commit

	  The number of internal COMMIT statements. This variable was added in
	  MySQL 4.0.2.

       ·  Handler_discover

	  The MySQL server can ask the NDB Cluster storage engine if it knows
	  about a table with a given name. This is called discovery.
	  Handler_discover indicates the number of times that tables have been
	  discovered. This variable was added in MySQL 4.1.2.

       ·  Handler_delete

	  The number of times a row was deleted from a table.

       ·  Handler_read_first

	  The number of times the first entry was read from an index. If this
	  value is high, it suggests that the server is doing a lot of full
	  index scans; for example, SELECT col1 FROM foo, assuming that col1
	  is indexed.

       ·  Handler_read_key

	  The number of requests to read a row based on a key. If this value
	  is high, it is a good indication that your tables are properly
	  indexed for your queries.

       ·  Handler_read_next

	  The number of requests to read the next row in key order. This value
	  is incremented if you are querying an index column with a range
	  constraint or if you are doing an index scan.

       ·  Handler_read_prev

	  The number of requests to read the previous row in key order. This
	  read method is mainly used to optimize ORDER BY ... DESC. This
	  variable was added in MySQL 3.23.6.

       ·  Handler_read_rnd

	  The number of requests to read a row based on a fixed position. This
	  value is high if you are doing a lot of queries that require sorting
	  of the result. You probably have a lot of queries that require MySQL
	  to scan entire tables or you have joins that don't use keys
	  properly.

       ·  Handler_read_rnd_next

	  The number of requests to read the next row in the data file. This
	  value is high if you are doing a lot of table scans. Generally this
	  suggests that your tables are not properly indexed or that your
	  queries are not written to take advantage of the indexes you have.

       ·  Handler_rollback

	  The number of internal ROLLBACK statements. This variable was added
	  in MySQL 4.0.2.

       ·  Handler_update

	  The number of requests to update a row in a table.

       ·  Handler_write

	  The number of requests to insert a row in a table.

       ·  Key_blocks_not_flushed

	  The number of key blocks in the key cache that have changed but have
	  not yet been flushed to disk. This variable was added in MySQL
	  4.1.1. It used to be known as Not_flushed_key_blocks.

       ·  Key_blocks_unused

	  The number of unused blocks in the key cache. You can use this value
	  to determine how much of the key cache is in use; see the discussion
	  of key_buffer_size in the section called “SYSTEM VARIABLES”. This
	  variable was added in MySQL 4.1.2.

       ·  Key_blocks_used

	  The number of used blocks in the key cache. This value is a
	  high-water mark that indicates the maximum number of blocks that
	  have ever been in use at one time.

       ·  Key_read_requests

	  The number of requests to read a key block from the cache.

       ·  Key_reads

	  The number of physical reads of a key block from disk. If Key_reads
	  is large, then your key_buffer_size value is probably too small. The
	  cache miss rate can be calculated as Key_reads/Key_read_requests.

       ·  Key_write_requests

	  The number of requests to write a key block to the cache.

       ·  Key_writes

	  The number of physical writes of a key block to disk.

       ·  Max_used_connections

	  The maximum number of connections that have been in use
	  simultaneously since the server started.

       ·  Not_flushed_delayed_rows

	  The number of rows waiting to be written in INSERT DELAY queues.

       ·  Not_flushed_key_blocks

	  The old name for Key_blocks_not_flushed before MySQL 4.1.1.

       ·  Open_files

	  The number of files that are open.

       ·  Open_streams

	  The number of streams that are open (used mainly for logging).

       ·  Open_tables

	  The number of tables that are open.

       ·  Opened_tables

	  The number of tables that have been opened. If Opened_tables is big,
	  your table_cache value is probably too small.

       ·  Qcache_free_blocks

	  The number of free memory blocks in the query cache.

       ·  Qcache_free_memory

	  The amount of free memory for the query cache.

       ·  Qcache_hits

	  The number of query cache hits.

       ·  Qcache_inserts

	  The number of queries added to the query cache.

       ·  Qcache_lowmem_prunes

	  The number of queries that were deleted from the query cache because
	  of low memory.

       ·  Qcache_not_cached

	  The number of non-cached queries (not cacheable, or not cached due
	  to the query_cache_type setting).

       ·  Qcache_queries_in_cache

	  The number of queries registered in the query cache.

       ·  Qcache_total_blocks

	  The total number of blocks in the query cache.

       ·  Questions

	  The number of statements that clients have sent to the server.

       ·  Rpl_status

	  The status of fail-safe replication (not yet implemented).

       ·  Select_full_join

	  The number of joins that perform table scans because they do not use
	  indexes. If this value is not 0, you should carefully check the
	  indexes of your tables. This variable was added in MySQL 3.23.25.

       ·  Select_full_range_join

	  The number of joins that used a range search on a reference table.
	  This variable was added in MySQL 3.23.25.

       ·  Select_range

	  The number of joins that used ranges on the first table. This is
	  normally not critical issue even if the value is quite large. This
	  variable was added in MySQL 3.23.25.

       ·  Select_range_check

	  The number of joins without keys that check for key usage after each
	  row. (If this is not equal to 0, you should very carefully check the
	  indexes of your tables.) This variable was added in MySQL 3.23.25.

       ·  Select_scan

	  The number of joins that did a full scan of the first table. This
	  variable was added in MySQL 3.23.25.

       ·  Slave_open_temp_tables

	  The number of temporary tables that the slave SQL thread currently
	  has open. This variable was added in MySQL 3.23.29.

       ·  Slave_running

	  This is ON if this server is a slave that is connected to a master.
	  This variable was added in MySQL 3.23.16.

       ·  Slave_retried_transactions

	  Total (since startup) number of times the replication slave SQL
	  thread has retried transactions. This variable was added in MySQL
	  4.1.11.

       ·  Slow_launch_threads

	  The number of threads that have taken more than slow_launch_time
	  seconds to create. This variable was added in MySQL 3.23.15.

       ·  Slow_queries

	  The number of queries that have taken more than long_query_time
	  seconds. See Section 10.5, “The Slow Query Log”.

       ·  Sort_merge_passes

	  The number of merge passes that the sort algorithm has had to do. If
	  this value is large, you should consider increasing the value of the
	  sort_buffer_size system variable. This variable was added in MySQL
	  3.23.28.

       ·  Sort_range

	  The number of sorts that were done with ranges. This variable was
	  added in MySQL 3.23.25.

       ·  Sort_rows

	  The number of sorted rows. This variable was added in MySQL 3.23.25.

       ·  Sort_scan

	  The number of sorts that were done by scanning the table. This
	  variable was added in MySQL 3.23.25.

       ·  Ssl_xxx

	  Variables used for SSL connections. These variables were added in
	  MySQL 4.0.0.

       ·  Table_locks_immediate

	  The number of times that a table lock was acquired immediately. This
	  variable was added in MySQL 3.23.33.

       ·  Table_locks_waited

	  The number of times that a table lock could not be acquired
	  immediately and a wait was needed. If this is high and you have
	  performance problems, you should first optimize your queries, and
	  then either split your table or tables or use replication. This
	  variable was added in MySQL 3.23.33.

       ·  Threads_cached

	  The number of threads in the thread cache. This variable was added
	  in MySQL 3.23.17.

       ·  Threads_connected

	  The number of currently open connections.

       ·  Threads_created

	  The number of threads created to handle connections. If
	  Threads_created is big, you may want to increase the
	  thread_cache_size value. The cache miss rate can be calculated as
	  Threads_created divided by Connections. This variable was added in
	  MySQL 3.23.31.

       ·  Threads_running

	  The number of threads that are not sleeping.

       ·  Uptime

	  The number of seconds that the server has been up.

SQL MODES
       The MySQL server can operate in different SQL modes, and (as of MySQL
       4.1) can apply these modes differentially for different clients. This
       capability enables each application to tailor the server's operating
       mode to its own requirements.

       Modes define what SQL syntax MySQL should support and what kind of data
       validation checks it should perform. This makes it easier to use MySQL
       in different environments and to use MySQL together with other database
       servers.

       You can set the default SQL mode by starting mysqld with the
       --sql-mode="modes" option.  modes is a list of different modes
       separated by comma (‘,’) characters. The default value is empty (no
       modes set). The modes value also can be empty (--sql-mode="") if you
       want to clear it explicitly.

       Beginning with MySQL 4.1, you can change the SQL mode at runtime by
       using a SET [GLOBAL|SESSION] sql_mode='modes' statement to set the
       sql_mode system value. Setting the GLOBAL variable requires the SUPER
       privilege and affects the operation of all clients that connect from
       that time on. Setting the SESSION variable affects only the current
       client. Any client can change its own session sql_mode value at any
       time.

       You can retrieve the current global or session sql_mode value with the
       following statements:

	  SELECT @@global.sql_mode;
	  SELECT @@session.sql_mode;

       The most important sql_mode value is ANSI, which changes syntax and
       behavior to be more conformant to standard SQL. This mode is available
       beginning in MySQL 4.1.1.

       The following list describes all supported modes:

       ·  ANSI_QUOTES

	  Treat ‘"’ as an identifier quote character (like the ‘`’ quote
	  character) and not as a string quote character. You can still use
	  ‘`’ to quote identifiers with this mode enabled. With ANSI_QUOTES
	  enabled, you cannot use double quotes to quote literal strings,
	  because it is interpreted as an identifier. (Added in MySQL 4.0.0)

       ·  IGNORE_SPACE

	  Allow spaces between a function name and the ‘(’ character. This
	  forces all function names to be treated as reserved words. As a
	  result, if you want to access any database, table, or column name
	  that is a reserved word, you must quote it. For example, because
	  there is a USER() function, the name of the user table in the mysql
	  database and the User column in that table become reserved, so you
	  must quote them:

	  SELECT "User" FROM mysql."user";
       (Added in MySQL 4.0.0)

       See Section 1.1, “MyISAM Startup Options”.

       ·  NO_AUTO_VALUE_ON_ZERO

	  NO_AUTO_VALUE_ON_ZERO affects handling of AUTO_INCREMENT columns.
	  Normally, you generate the next sequence number for the column by
	  inserting either NULL or 0 into it.  NO_AUTO_VALUE_ON_ZERO
	  suppresses this behavior for 0 so that only NULL generates the next
	  sequence number. (Added in MySQL 4.1.1)

	  This mode can be useful if 0 has been stored in a table's
	  AUTO_INCREMENT column. (Storing 0 is not a recommended practice, by
	  the way.) For example, if you dump the table with mysqldump and then
	  reload it, MySQL normally generates new sequence numbers when it
	  encounters the 0 values, resulting in a table with contents
	  different from the one that was dumped. Enabling
	  NO_AUTO_VALUE_ON_ZERO before reloading the dump file solves this
	  problem. As of MySQL 4.1.1, mysqldump automatically includes a
	  statement in the dump output that enables NO_AUTO_VALUE_ON_ZERO to
	  avoid this problem.

       ·  NO_DIR_IN_CREATE

	  When creating a table, ignore all INDEX DIRECTORY and DATA DIRECTORY
	  directives. This option is useful on slave replication servers.
	  (Added in MySQL 4.0.15)

       ·  NO_FIELD_OPTIONS

	  Do not print MySQL-specific column options in the output of SHOW
	  CREATE TABLE. This mode is used by mysqldump in portability mode.
	  (Added in MySQL 4.1.1)

       ·  NO_KEY_OPTIONS

	  Do not print MySQL-specific index options in the output of SHOW
	  CREATE TABLE. This mode is used by mysqldump in portability mode.
	  (Added in MySQL 4.1.1)

       ·  NO_TABLE_OPTIONS

	  Do not print MySQL-specific table options (such as ENGINE) in the
	  output of SHOW CREATE TABLE. This mode is used by mysqldump in
	  portability mode. (Added in MySQL 4.1.1)

       ·  NO_UNSIGNED_SUBTRACTION

	  In integer subtraction operations, do not mark the result as
	  UNSIGNED if one of the operands is unsigned. In other words, the
	  result of a subtraction is always signed whenever this mode is in
	  effect, even if one of the operands is unsigned. For example,
	  compare the type of column c2 in table t1 with that of column c2 in
	  table t2:

	  mysql> SET SQL_MODE='';
	  mysql> CREATE TABLE test (c1 BIGINT UNSIGNED NOT NULL);
	  mysql> CREATE TABLE t1 SELECT c1 - 1 AS c2 FROM test;
	  mysql> DESCRIBE t1;
	  +-------+---------------------+------+-----+---------+-------+
	  | Field | Type		| Null | Key | Default | Extra |
	  +-------+---------------------+------+-----+---------+-------+
	  | c2	  | bigint(21) unsigned |      |     | 0       |       |
	  +-------+---------------------+------+-----+---------+-------+
	  mysql> SET SQL_MODE='NO_UNSIGNED_SUBTRACTION';
	  mysql> CREATE TABLE t2 SELECT c1 - 1 AS c2 FROM test;
	  mysql> DESCRIBE t2;
	  +-------+------------+------+-----+---------+-------+
	  | Field | Type       | Null | Key | Default | Extra |
	  +-------+------------+------+-----+---------+-------+
	  | c2	  | bigint(21) |      |	    | 0	      |	      |
	  +-------+------------+------+-----+---------+-------+
       Note that this means that BIGINT UNSIGNED is not 100% usable in all
       contexts. See Section 8, “Cast Functions and Operators”. (Added in
       MySQL 4.0.2)

	  mysql> SET SQL_MODE = '';
	  mysql> SELECT CAST(0 AS UNSIGNED) - 1;
	  +-------------------------+
	  | CAST(0 AS UNSIGNED) - 1 |
	  +-------------------------+
	  |    18446744073709551615 |
	  +-------------------------+
	  mysql> SET SQL_MODE = 'NO_UNSIGNED_SUBTRACTION';
	  mysql> SELECT CAST(0 AS UNSIGNED) - 1;
	  +-------------------------+
	  | CAST(0 AS UNSIGNED) - 1 |
	  +-------------------------+
	  |			 -1 |
	  +-------------------------+

       ·  ONLY_FULL_GROUP_BY

	  Do not allow queries for which the SELECT list refers to
	  non-aggregated columns that are not named in the GROUP BY clause.
	  (Added in MySQL 4.0.0) The following query is invalid with this mode
	  enabled because address is not named in the GROUP BY clause:

	  SELECT name, address, MAX(age) FROM t GROUP BY name;

       ·  PIPES_AS_CONCAT

	  Treat || as a string concatenation operator (same as CONCAT())
	  rather than as a synonym for OR. (Added in MySQL 4.0.0)

       ·  REAL_AS_FLOAT

	  Treat REAL as a synonym for FLOAT. By default, MySQL treats REAL as
	  a synonym for DOUBLE. (Added in MySQL 4.0.0)

       The following special modes are provided as shorthand for combinations
       of mode values from the preceding list. All are available as of MySQL
       4.1.1.

       The descriptions include all mode values that are available in the most
       recent version of MySQL. For older versions, a combination mode does
       not include individual mode values that are not available except in
       newer versions.

       ·  ANSI

	  Equivalent to REAL_AS_FLOAT, PIPES_AS_CONCAT, ANSI_QUOTES,
	  IGNORE_SPACE. Before MySQL 4.1.11, ANSI also includes
	  ONLY_FULL_GROUP_BY. See Section 9.3, “Running MySQL in ANSI Mode”.

       ·  DB2

	  Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE,
	  NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.

       ·  MAXDB

	  Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE,
	  NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.

       ·  MSSQL

	  Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE,
	  NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.

       ·  MYSQL323

	  Equivalent to NO_FIELD_OPTIONS.

       ·  MYSQL40

	  Equivalent to NO_FIELD_OPTIONS.

       ·  ORACLE

	  Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE,
	  NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.

       ·  POSTGRESQL

	  Equivalent to PIPES_AS_CONCAT, ANSI_QUOTES, IGNORE_SPACE,
	  NO_KEY_OPTIONS, NO_TABLE_OPTIONS, NO_FIELD_OPTIONS.

THE SHUTDOWN PROCESS
       The server shutdown process takes place as follows:

       1. The shutdown process is initiated.

	  Server shutdown can be initiated several ways. For example, a user
	  with the SHUTDOWN privilege can execute a mysqladmin shutdown
	  command.  mysqladmin can be used on any platform supported by MySQL.
	  Other operating system-specific shutdown initiation methods are
	  possible as well: The server shuts down on Unix when it receives a
	  SIGTERM signal. A server running as a service on Windows shuts down
	  when the services manager tells it to. (On Windows, a user with
	  Administrator rights can also shut down the server using NET STOP
	  service_name, where service_name is the name of the MySQL service.
	  By default, this is MySQL.)

       2. The server creates a shutdown thread if necessary.

	  Depending on how shutdown was initiated, the server might create a
	  thread to handle the shutdown process. If shutdown was requested by
	  a client, a shutdown thread is created. If shutdown is the result of
	  receiving a SIGTERM signal, the signal thread might handle shutdown
	  itself, or it might create a separate thread to do so. If the server
	  tries to create a shutdown thread and cannot (for example, if memory
	  is exhausted), it issues a diagnostic message that appears in the
	  error log:

	  Error: Can't create thread to kill server

       3. The server stops accepting new connections.

	  To prevent new activity from being initiated during shutdown, the
	  server stops accepting new client connections. It does this by
	  closing the network connections to which it normally listens for
	  connections: the TCP/IP port, the Unix socket file, the Windows
	  named pipe, and shared memory on Windows.

       4. The server terminates current activity.

	  For each thread that is associated with a client connection, the
	  connection to the client is broken and the thread is marked as
	  killed. Threads die when they notice that they are so marked.
	  Threads for idle connections die quickly. Threads that currently are
	  processing statements check their state periodically and take longer
	  to die. For additional information about thread termination, see
	  Section 5.5.3, “KILL Syntax”, in particular for the instructions
	  about killed REPAIR TABLE or OPTIMIZE TABLE operations on MyISAM
	  tables.

	  For threads that have an open transaction, the transaction is rolled
	  back. Note that if a thread is updating a non-transactional table,
	  an operation such as a multiple-row UPDATE or INSERT may leave the
	  table partially updated, because the operation can terminate before
	  completion.

	  If the server is a master replication server, threads associated
	  with currently connected slaves are treated like other client
	  threads. That is, each one is marked as killed and exits when it
	  next checks its state.

	  If the server is a slave replication server, the I/O and SQL
	  threads, if active, are stopped before client threads are marked as
	  killed. The SQL thread is allowed to finish its current statement
	  (to avoid causing replication problems), and then stops. If the SQL
	  thread was in the middle of a transaction at this point, the
	  transaction is rolled back.

       5. Storage engines are shut down or closed.

	  At this stage, the table cache is flushed and all open tables are
	  closed.

	  Each storage engine performs any actions necessary for tables that
	  it manages. For example, MyISAM flushes any pending index writes for
	  a table.  InnoDB flushes its buffer pool to disk, writes the current
	  LSN to the tablespace, and terminates its own internal threads.

       6. The server exits.

SERVER-SIDE HELP
       As of MySQL 4.1, MySQL Server supports a HELP statement that returns
       online information from the MySQL Reference manual (see Section 3.2,
       “HELP Syntax”). The proper operation of this statement requires that
       the help tables in the mysql database be initialized with help topic
       information, which is done by processing the contents of the
       fill_help_tables.sql script.

       For a MySQL binary distribution on Unix, help table setup occurs when
       you run mysql_install_db. For an RPM distribution on Linux or binary
       distribution on Windows, help table setup occurs as part of the MySQL
       installation process.

       For a MySQL source distribution, you can find the fill_help_tables_sql
       file in the scripts directory. To load the file manually, make sure
       that you have initialized the mysql database by running
       mysql_install_db, and then process the file with the mysql client as
       follows:

	  shell> mysql -u root mysql < fill_help_tables.sql

       If you are working with BitKeeper and a MySQL development source tree,
       the tree doesn't contain fill_help_tables.sql. You can download the
       proper file for your version of MySQL from http://dev.mysql.com/doc/.
       After downloading and uncompressing the file, process it with mysql as
       just described.

COPYRIGHT
       Copyright 1997-2006 MySQL AB

       This documentation is NOT distributed under a GPL license. Use of this
       documentation is subject to the following terms: You may create a
       printed copy of this documentation solely for your own personal use.
       Conversion to other formats is allowed as long as the actual content is
       not altered or edited in any way. You shall not publish or distribute
       this documentation in any form or on any media, except if you
       distribute the documentation in a manner similar to how MySQL
       disseminates it (that is, electronically for download on a Web site
       with the software) or on a CD-ROM or similar medium, provided however
       that the documentation is disseminated together with the software on
       the same medium. Any other use, such as any dissemination of printed
       copies or use of this documentation, in whole or in part, in another
       publication, requires the prior written consent from an authorized
       representative of MySQL AB. MySQL AB reserves any and all rights to
       this documentation not expressly granted above.

       Please email <docs@mysql.com> for more information.

SEE ALSO
       isamchk(1), isamlog(1), msql2mysql(1), myisam_ftdump(1), myisamchk(1),
       myisamlog(1), myisampack(1), mysql(1), mysql.server(1),
       mysql_config(1), mysql_explain_log(1), mysql_fix_privilege_tables(1),
       mysql_zap(1), mysqlaccess(1), mysqladmin(1), mysqlbinlog(1),
       mysqlcheck(1), mysqld(1), mysqld_multi(1), mysqld_safe(1),
       mysqldump(1), mysqlhotcopy(1), mysqlimport(1), mysqlshow(1),
       pack_isam(1), perror(1), replace(1), safe_mysqld(1)

       For more information, please refer to the MySQL Reference Manual, which
       may already be installed locally and which is also available online at
       http://dev.mysql.com/doc/.

AUTHOR
       MySQL AB (http://www.mysql.com/).  This software comes with no
       warranty.

MySQL 4.1			  11/02/2006			     MYSQLD(8)
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