semmnu man page on HP-UX

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semmnu(5)							     semmnu(5)

NAME
       semmnu - maximum number of System V IPC undo structures for processes

VALUES
   Failsafe
   Default
   Allowed values
DESCRIPTION
       Note:  If the DynSysVSem optional product bundle is installed then this
       tunable is ignored and has no effect.  Applications can perform	"undo"
       operations without any system imposed limits.

       The  tunable  specifies	the maximum number of System V IPC system-wide
       processes that can have "undo" operations pending at any given time.

       If an application exhausts this limit, it will receive an error from

       For more information about System V semaphores, refer to the section of
       the sema(5) manpage.

   Who Is Expected to Change This Tunable?
       Anyone.

   Restrictions on Changing
       Changes to this tunable take effect at the next reboot.

       Note:   If  the	DynSysVSem  optional  product bundle is installed then
       changes to this tunable are ignored and have no effect.

   When Should the Value of This Tunable Be Raised?
       When the set of application processes which use semaphore "undo" seman‐
       tics exceeds the limit.

   When Should the Value of This Tunable Be Lowered?
       If  requirements	 for  semaphore	 "undo"	 semantics  has	 significantly
       decreased, or for limiting protection on	 run-away  applications	 which
       change semaphores.

   What Other Tunable Values Should Be Changed at the Same Time?
       All  the System V semaphore tunables are interrelated and should not be
       treated as independent variables.  The tunables must be evaluated as  a
       system  to ensure they reflect the application requirements.  The sema‐
       phore tunables include and Generally, a	change	in  does  not  require
       attention to other tunables.

       Note:   If the DynSysVSem optional product bundle is installed then the
       and tunables are ignored and have no effect.

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

       A two-dimensional table of undo structures (~8 bytes each) is allocated
       in  kernel memory at boot time.	This memory is reserved whether or not
       it is used.

       The table dimensions are and (maximum number of per-process undo struc‐
       tures).	 So  the  memory  requirement  is approximately the product of
       those two tunables and the structure size.  Use care when setting these
       two tunables, as they can have a profound effect on memory utilization,
       due to the multiplicative effect.

       Note:  If the DynSysVSem optional product bundle is installed then  and
       are  ignored  and have no effect.  No memory is allocated at boot time.
       Instead "undo" structures are dynamically allocated when needed by  the
       application and deallocated when no longer needed.

       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

AUTHOR
       was developed by AT&T.

SEE ALSO
       semop(2),   sema(5),   semaem(5),   semmns(5),	semmni(5),  semmsl(5),
       semume(5), semvmx(5), sysv_hash_locks(5).

			   Tunable Kernel Parameters		     semmnu(5)
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