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Tunable Kernel Parameters
HP-UX 11i Version 3: February 2007

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semaem — adjust-on-exit maximum value






Allowed values

Minimum: 0

Maximum: semvmx or less than or equal to 32767.


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?


Restrictions on Changing

Changes to this tunable 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 increments, 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 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, the semvmx and the semaem values may need adjustment together.


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.


semaem was developed by AT&T.

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