semvmx(5)                                                         semvmx(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      semvmx - maximum value of any single System V IPC semaphore

 VALUES    [Toc]    [Back]
    Failsafe
      32767

    Default    [Toc]    [Back]
      32767

    Allowed values    [Toc]    [Back]
      Minimum: 1

      Maximum: 65535

 DESCRIPTION    [Toc]    [Back]
      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    [Toc]    [Back]
      Changes to this tunable 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 variables.  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.

 WARNINGS    [Toc]    [Back]
      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.



 Hewlett-Packard Company            - 1 -      HP-UX 11i Version 2: Sep 2004






 semvmx(5)                                                         semvmx(5)
                          Tunable Kernel Parameters



      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
      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://docs.hp.com.

 AUTHOR    [Toc]    [Back]
      semvmx was developed by AT&T.

 SEE ALSO    [Toc]    [Back]
      semop(2), semctl(2), sema(5), semaem(5), semmni(5), semmns(5),
      semmnu(5), semmsl(5), semume(5), sysv_hash_locks(5).


 Hewlett-Packard Company            - 2 -      HP-UX 11i Version 2: Sep 2004