NAME
semmni — number of System V IPC system-wide semaphore identifiers
VALUES
Allowed values
Minimum: 2
Maximum: semmns.
DESCRIPTION
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)
semaphores.
If an application attempts to create a semaphore set when
all IDs have previously been allocated, it will receive an
ENOSPC
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.
Restrictions on Changing
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,
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
sysv_hash_locks
tunable.
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 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
semmni
was developed by AT&T.
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