Tunable Kernel Parameters
NAME [Toc] [Back]
semmni - number of System V IPC system-wide semaphore identifiers
VALUES [Toc] [Back]
Default [Toc] [Back]
Allowed values [Toc] [Back]
DESCRIPTION [Toc] [Back]
The semmni tunable specifies the maximum number of System V IPC
system-wide semaphore sets (and identifiers) which can exist at any
given time. A single identifier (ID) is returned for each semget()
system call to create a new set of one or more (up to semmsl)
If an application attempts to create a semaphore set when all IDs have
previously been allocated, 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 there is a requirement of more total unique semaphore IDs in the
system, or one or more applications require more semaphore IDs. There
is no reason to specify more system-wide identifiers than the total of
the semmns semaphores.
When Should the Value of This Tunable Be Lowered?
If requirements for semaphore sets (IDs) has significantly decreased,
or there is a need to hard-limit applications from acquiring larger
numbers of semaphore IDs.
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,
Hewlett-Packard Company - 1 - HP-UX 11i Version 2: Sep 2004
Tunable Kernel Parameters
semume, semvmx, and sysv_hash_locks. Specifically, changes in the
semmni tunable may also require changes in the semmns tunable. Very
significant changes in semmni may also require changes in the
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]
semmni was developed by AT&T.
SEE ALSO [Toc] [Back]
semget(2), sema(5), semaem(5), semmns(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 ]