Tunable Kernel Parameters
NAME [Toc] [Back]
semmns - number of System V IPC system-wide semaphores
VALUES [Toc] [Back]
Default [Toc] [Back]
Allowed values [Toc] [Back]
DESCRIPTION [Toc] [Back]
The semmns tunable specifies the maximum total individual System V IPC
system-wide semaphores which can be assigned by applications.
Semaphores are assigned in "sets" associated with an ID. Thus
semaphores can be distributed in any manner across the range of IDs
with one or more per ID.
There is no reason to specify semmns less than semmni (the maximum
number of identifiers) as each ID requires at least one semaphore.
If an application attempts to create a semaphore set with more
semaphores than are remaining, it will receive an [ENOSPC] error from
For more information about System V semaphores, refer to the Overview
section of the sema(5) manpage.
Who Is Expected to Change This Tunable?
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 applications require more total semaphores in the system.
When Should the Value of This Tunable Be Lowered?
If requirements for semaphores has decreased, or there is a need to
hard-limit applications from acquiring larger numbers of 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. Typically, a change in the
Hewlett-Packard Company - 1 - HP-UX 11i Version 2: Sep 2004
Tunable Kernel Parameters
semmns tunable does not require changes to other tunables.
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.
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
AUTHOR [Toc] [Back]
semmns was developed by AT&T.
SEE ALSO [Toc] [Back]
semget(2), sema(5), semaem(5), semmni(5), semmnu(5), semmsl(5),
semume(5), semvmx(5), sysv_hash_locks(5).
Hewlett-Packard Company - 2 - HP-UX 11i Version 2: Sep 2004 [ Back ]