semmns(5)semmns(5)NAMEsemmns - number of System V IPC system-wide semaphores
VALUES
Failsafe
Default
Allowed values
DESCRIPTION
The 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 dis‐
tributed in any manner across the range of IDs with one or more per ID.
There is no reason to specify less than (the maximum number of identi‐
fiers) as each ID requires at least one semaphore.
If an application attempts to create a semaphore set with more sema‐
phores than are remaining, it will receive an error from
For more information about System V semaphores, refer to the 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.
Note: If the DynSysVSem optional product bundle is installed then
changes to this tunable take effect immediately.
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 Are the Side Effects of Lowering the Value?
The following side effect applies only if the DynSysVSem optional prod‐
uct bundle is installed.
If DynSysVSem is installed, lowering the value of this tunable
increases the risk of application failure due to the inability to cre‐
ate more semaphore sets. Lowering the tunable has no effect on any
active semaphores in their respective sets, even if the new tunable
value is less than the number of semaphores already created on the sys‐
tem. However, no new semaphore sets may be created until the number of
active semaphores on the system falls below the setting of
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 sema‐
phore tunables include and Typically, a change in the tunable does not
require changes to other tunables.
Note: If the DynSysVSem optional product bundle is installed then the
and tunables are ignored and have no effect.
WARNINGS
All HP-UX kernel tunable parameters are release specific. This parame‐
ter 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 val‐
ues. For information about the effects of installation on tunable val‐
ues, consult the documentation for the kernel software being installed.
For information about optional kernel software that was factory
installed on your system, see at
AUTHOR
was developed by AT&T.
SEE ALSOsemget(2), sema(5), semaem(5), semmni(5), semmnu(5), semmsl(5),
semume(5), semvmx(5), sysv_hash_locks(5).
Tunable Kernel Parameters semmns(5)
