NAME
sema — enable or disable System V IPC semaphores at boot time
DESCRIPTION
The
sema
tunable is obsolete. The System V IPC semaphore subsystem is always enabled.
Overview
System V IPC is comprised of mechanisms for arbitrary processes to send and
receive data messages, share virtual address space and use semaphores
to synchronize execution.
A System V semaphore is a synchronization method for user processes to
synchronize or serialize access to common data and resources.
Each semaphore "set" has an ID, but each set can contain one or more
independent semaphores.
Semaphore sets are created or initially accessed
through
semget()
using an application-specified "key", which can be generated by
ftok().
Operations on the set are performed through
semop()
and
semctl().
Semaphore sets are removed through
semctl()
or the
ipcrm
command.
WARNINGS
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.
AUTHOR
sema
was developed by AT&T.
SEE ALSO
ipcs(1),
ipcrm(1),
semget(2),
semop(2),
semctl(2),
semaem(5),
semmni(5),
semmns(5),
semmnu(5),
semmsl(5),
semume(5),
semvmx(5),
sysv_hash_locks(5).
