msgmni(5)

NAME

msgmni — maximum number of system-wide System V IPC message queues (IDs) allowed

VALUES

Default

512

Failsafe

512

Allowed Values

Minimum: 1

Maximum: 32767

DESCRIPTION

The msgmni tunable specifies the maximum number of system-wide System V IPC message queue identifiers (one per queue). Each message queue created has an identifier (ID) and there is an upper limit of msgmni identifiers.

Applications use the msgget() system call to create new queues. If all IDs have been used, msgget() will return ENOSPC.

If a process acquires a message queue, but the process terminates without removing it, the queue and all its messages remain. Abandoned message queues can be removed with the ipcrm command. Message queue status can be monitored using the ipcs command.

For more information about System V message queues, refer to the Overview section of the mesg(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?

Raise this tunable when applications require more queues.

When Should the Value of This Tunable Be Lowered?

Lower this tunable when the requirement for queues has diminished.

What Other Tunable Values Should Be Changed at the Same Time?

All the System V message queue tunables are interrelated and should not be treated as independent variables. The set must be evaluated as a system to ensure the tunables reflect the application requirements. The message tunables include msgmap, msgmax, msgmnb, msgmni, msgseg, msgssz, and msgtql. Specifically, the msgseg and msgtql tunables, may need adjustment along with changes to the msgmni tunable.

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 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

msgmni was developed by AT&T.