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semvmx.5 (2010 09)

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semvmx(5) semvmx(5)
(Tunable Kernel Parameters)
NAME
semvmx - maximum value of any single System V IPC semaphore
VALUES
Failsafe
32767
Default
32767
Allowed values
Minimum: 1
Maximum: 65535
DESCRIPTION
The semvmx tunable specifies the maximum value any given System V IPC semaphore can have.
If an application attempt to exceed this limit, it will receive an [ERANGE] error from
semop() or from
semctl().
For more information about System V semaphores, refer to the Overview 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 increases in the tunable value take effect
immediately; decreases in the tunable value take effect at the next reboot.
When Should the Value of This Tunable Be Raised?
If an application requires larger semaphore values.
When Should the Value of This Tunable Be Lowered?
If requirements for the single semaphore value has decreased, or if there for limit 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 vari-
ables. The tunables must be evaluated as a system to ensure they reflect the application requirements.
The semaphore tunables include
semaem, semmni, semmns, semmnu, semmsl, semume, semvmx
, and
sysv_hash_locks. Consider changes to
semaem when changing semvmx.
Note: If the DynSysVSem optional product bundle is installed then the
semmnu, semume, and
sysv_hash_locks tunables are ignored and have no effect.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parameter may be removed or have its
meaning changed in future releases of HP-UX.
Installation of optional kernel software, from HP or other vendors, may cause changes to tunable parame-
ter values. After installation, some tunable parameters may no longer be at the default or recommended
values. For information about the effects of installation on tunable values, consult the documentation for
the kernel software being installed. For information about optional kernel software that was factory
installed on your system, see HP-UX Release Notes at http://www.hp.com/go/hpux-core-docs.
AUTHOR
semvmx was developed by AT&T.
SEE ALSO
kctune(1M), semop(2), semctl(2), sema(5), semaem(5), semmni(5), semmns(5), semmnu(5), semmsl(5),
semume(5), sysv_hash_locks(5).
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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