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semaem.5 (2010 09)

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semaem(5) semaem(5)
(Tunable Kernel Parameters)
NAME
semaem - adjust-on-exit maximum value
VALUES
Failsafe
16384
Default
16384
Allowed values
Minimum: 0
Maximum: semvmx or less than or equal to
32767.
DESCRIPTION
The
semaem tunable specifies maximum cumulative "undo" value for any one semaphore as changed any
one single process. That is, a process is allowed up to
semaem outstanding increments or decrements on
a semaphore for which
SEM_UNDO has been specified.
If an application attempts to exceed the limit, it will receive an [ERANGE] error from
semop().
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.
Note: If the DynSysVSem optional product bundle is installed increases in the tunable value take effect
immediately; decreases in the tunable value take effect at the next reboot.
When Should the Value of This Tunable Be Raised?
When an application is expected to have large increments or decrements of a semaphore, or a large series
of increments without intervening decrements, or a large series of decrements without intervening incre-
ments, for which "undo" semantics are desired.
When Should the Value of This Tunable Be Lowered?
When applications no longer have the need for a raised value.
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 vari-
ables. 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, the semvmx and the semaem values may need adjustment together.
Note: If the DynSysVSem optional product bundle is installed then the
semmnu, semume, and
sysv_hash_locks tunables are ignored and have no effect.
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 parame-
ter 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://www.hp.com/go/hpux-core-docs.
AUTHOR
semaem was developed by AT&T.
SEE ALSO
kctune(1M), semop(2), sema(5), semmni(5), semmns(5), semmnu(5), semmsl(5), semume(5), semvmx(5),
sysv_hash_locks(5).
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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