NAME
msgmni — maximum number of system-wide System V IPC message queues (IDs) allowed
VALUES
Allowed Values
Minimum: 1
Maximum: 1,000,000
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
This tunable is dynamic.
Changes to to this tunable take effect immediately.
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 are the Side Effects of Lowering the Value?
Lowering the value increases the risk of application failure due
to the inability to create more message queues.
Lowering the tunable has no effect on any active message
queues, even if the new tunable value is less than the number
of queues created in the system. However, no new queues may be
created until the number of active queues falls below the
setting of
msgmni.
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
msgmbs,
msgmnb,
msgmni,
and
msgtql.
Specifically,
msgtql
and
msgmbs
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.
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