sema.5 (2010 09)

sema(5) sema(5)

(Tunable Kernel Parameters)

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sema tunable is obsolete.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 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

sema was developed by AT&T.