HP-UX Reference (11i v2 07/12) - 5 Miscellaneous (vol 9)

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msgtql(5) msgtql(5)
(Tunable Kernel Parameters)
NAME
msgtql - maximum number of System V IPC messages in the system at any time
VALUES
Default
1024
Failsafe
1024
Allowed values
Minimum: 1
Maximum: msgseg
Recommended values
The largest number of messages expected.
DESCRIPTION
The msgtql tunable specifies the maximum total system-wide individual messages across all message
queues. Every message has a header to specify message type and location and the total number of headers
is limited by msgtql.
Note that if a msgsnd() system call attempts to exceed the limit imposed by msgtql, it will block until
message space becomes available or return [EAGAIN] if
IPC_NOWAIT is set.
Other kernel tunables may limit the maximum number of messages supported. Limiting factors can be
msgmnb, the maximum number of bytes in a queue, or msgseg, the maximum number of message seg-
ments.
For more information about System V message queues, refer to the Overview section of the mesg(5) man-
page.
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 if applications block too frequently in
msgsnd(), requiring more total messages be held
in the kernel message queues.
When Should the Value of This Tunable Be Lowered?
Lower this tunable when applications no longer require as many total messages.
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 vari-
ables. 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 or msgssz tunables may need to be adjusted along with the msgtql 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 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
msgtql was developed by AT&T.
258 Hewlett-Packard Company − 1 − HP-UX 11i Version 2: December 2007 Update