HP-UX Reference (11i v3 07/02) - 5 Miscellaneous Topics (vol 9)

ManualsBrandsHP ManualsSoftwareHP-UX Reference Manuals

451

452

453

454

455

456

457

458

459

460

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.

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 variables.

The tunables must be evaluated as a system to ensure they reﬂect the application requirements. The sema-

phore tunables include

semaem, semmni, semmns, semmnu, semmsl, semume, semvmx

, and

sysv_hash_locks. Speciﬁcally, the

semvmx and the semaem values may need adjustment together.

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://docs.hp.com.

AUTHOR

semaem was developed by AT&T.