dontdump man page on HP-UX

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dontdump(5)							   dontdump(5)

       dontdump	 - defines which classes of kernel memory pages are not dumped
       when a kernel panic occurs

       (Allow the kernel to choose which classes to dump.)

   Allowed values
       Integer values from to

       The integer value should be the sum  of	the  integer  values  for  the
       excluded classes as follows:

	      2 : Unused pages
	      4 : User pages
	      8 : Buffer cache
	      16 : Kernel text pages
	      32 : Process stack
	      64 : File-system Metadata
	      128 : Kernel dynamic data
	      256 : Kernel static data
	      512 : Unused superpage pool

   Recommended values
       (Allow the kernel to choose which classes to dump.)

       The  value  the	kernel	usually	 chooses is = The kernel chooses these
       classes because they are not usually useful in debugging	 kernel	 prob‐

       On large systems, the time required to dump system memory when a kernel
       panic occurs can be excessive or even  prohibitive,  depending  on  how
       much  physical  memory is installed in the system.  Fast-dump capabili‐
       ties controlled by the and parameters provide a means  for  restricting
       kernel dumps to specific types of information:

	       . Unused Physical Memory
	       . User Process
	       . Buffer Cache
	       . Kernel Code
	       . Process Stack
	       . File-System Metadata
	       . Kernel Dynamic Data
	       . Kernel Static Data
	       . Unused Superpage Pool

       The  command,  and  its	associated configuration file control which of
       these memory classes are to be included in the memory dumps  associated
       with  a	kernel	panic.	On rare occasions, the system may panic before
       crashconf(1M) is run during the boot process.  On those occasions,  the
       configuration can be set using the and tunables.

       The bit-map value stored in specifies which of these memory classes are
       not to be included in the memory dumps associated with a kernel panic.

       The default value for this parameter is The system  determines  whether
       or  not	to  dump  classes  of  memory  based on the type of crash that
       occurs, in this case.

       Note that certain types of system crash, require	 a  full  crash	 dump.
       Also, the system operator may request a full crash dump at the time the
       dump is taken.  In either of these cases, a full dump will be performed
       regardless of the classes selected using

   Who Is Expected to Change This Tunable?
       Only HP Field engineers should change the value of this tunable.

   Restrictions on Changing
       Changes	to  this tunable take effect at next reboot. Use to change the
       selection of pages to take effect immediately.

   When Should the Tunable Be Turned On?
       This tunable should be turned on to exclude certain  classes  of	 pages
       from  being  dumped  when there is a system crash.  This can be done to
       speedup the dump.

   What Are the Side Effects of Turning the Tunable On?
       If pages necessary for analyzing the dump are excluded, then  the  dump
       may not be useful for identifying the cause of the system crash.

   When Should the Tunable Be Turned Off?
       The tunable is turned off by default.

   What Are the Side Effects of Turning the Tunable Off?
       The  system  decides  the page classes that must not be dumped based on
       the type of crash.  The dump may take longer.

   What Other Tunables Should Be Changed at the Same Time?
       The tunable should not contain the same page classes as

       All HP-UX kernel tunable parameters are release specific.  This parame‐
       ter  may	 be  removed or have its meaning changed in future releases of

       Installation of optional kernel software, from HP or other vendors, may
       cause  changes  to  tunable parameter values.  After installation, some
       tunable parameters may no longer be at the default or recommended  val‐
       ues.  For information about the effects of installation on tunable val‐
       ues, consult the documentation for the kernel software being installed.
       For  information	 about	optional  kernel  software  that  was  factory
       installed on your system, see at

       was developed by HP.

       crashconf(1M), alwaysdump(5).

			   Tunable Kernel Parameters		   dontdump(5)

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