semmsl(5)                                                         semmsl(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      semmsl - maximum number of System V IPC semaphores per identifier

 VALUES    [Toc]    [Back]
    Failsafe
      2048

    Default    [Toc]    [Back]
      2048

    Allowed values    [Toc]    [Back]
      Minimum: 1

      Maximum: 10240

 DESCRIPTION    [Toc]    [Back]
      The semmsl tunable specifies the maximum number of individual System V
      IPC semaphores per semaphore identifier (ID).

      If an application attempts to exceed this limit, it will receive an
      [EINVAL] error from semget().

      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.

    When Should the Value of This Tunable Be Raised?
      If applications require a larger number of semaphores per ID.

    When Should the Value of This Tunable Be Lowered?
      If application requirements for semaphores per ID has decreased or
      there is a need to protect against ill-behaved applications.

    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.  Specifically, a change in the
      semmsl tunable may require a change in the semmns tunable.

 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.

      Prior to HP-UX 11i Version 1 the maximum number of semaphores per ID
      was an undocumented constant 2048 in the header file sys/sem.h.
      Typically applications do not depend upon this limitation.  For those



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






 semmsl(5)                                                         semmsl(5)
                          Tunable Kernel Parameters



      that were compiled with the old constant, semmsl tunable values higher
      than 2048 will generally not be a problem.  However, semmsl tunable
      values lower than 2048 may cause other such applications to fail.
      These should be recoded to obtain the current semmsl value from
      pstat_getipc(2).

      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]
      semmsl was developed by AT&T.

 SEE ALSO    [Toc]    [Back]
      semget(2), sema(5), semaem(5), semmns(5), semmni(5), semmnu(5),
      semume(5), semvmx(5), sysv_hash_locks(5).


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