semume(5)semume(5)NAMEsemume - maximum number of System V IPC undo entries per process
VALUES
Failsafe
Default
Allowed values
DESCRIPTION
Note: If the DynSysVSem optional product bundle is installed then this
tunable is ignored and has no effect. Applications can perform "undo"
operations without any system imposed limits.
The tunable specifies the maximum number of System V IPC semaphores
upon which a single process can have outstanding (non-zero) "undo"
operations.
If an application exhausts this limit, 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 are ignored and have no effect.
When Should the Value of This Tunable Be Raised?
If applications require more semaphore undo operations per process.
When Should the Value of This Tunable Be Lowered?
If per-process requirements for semaphore operation has significantly
decreased, or if there for limit protection on run-away applications
which change semaphores.
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 does not require
attention to other tunables. However, changes to or might require
changes to if individual application processes are expected to use
fewer or more semaphores with "undo" semantics.
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.
A two-dimensional table of undo structures (~8 bytes each) is allocated
in kernel memory at boot time. This memory is reserved whether or not
it is used.
The table dimensions are and (maximum number of per-process undo struc‐
tures). So the memory requirement is approximately the product of
those two tunables and the structure size. Use care when setting these
two tunables, as they can have a profound effect on memory utilization,
due to the multiplicative effect.
Note: If the DynSysVSem optional product bundle is installed then and
are ignored and have no effect. No memory is allocated at boot time.
Instead "undo" structures are dynamically allocated when needed by the
application and deallocated when no longer needed.
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 ALSOsemop(2), sema(5), semaem(5), semmni(5), semmnu(5), semmsl(5),
semmns(5), semvmx(5), sysv_hash_locks(5).
Tunable Kernel Parameters semume(5)