NAME
msgmnb — maximum number of bytes on a single System V IPC message queue
VALUES
Allowed Values
Minimum: 0
Maximum: 0x4000000
DESCRIPTION
The
msgmnb
tunable specifies the maximum allowable total combined size, in bytes,
of all messages queued in a single given System V IPC message queue
at any one time.
If a
msgsnd()
system call attempts to exceed the limit imposed by
msgmnb,
it will block (or return
EAGAIN
if
IPC_NOWAIT
was specified) until a caller of
msgrcv()
decreases the number of bytes in the queue sufficiently
such that the new message, along with other messages still
on the queue, will fit within the
msgmnb
limit.
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 affect subsequent
msgsnd()
operations.
When Should the Value of This Tunable Be Raised?
Raise this tunable if applications have a need to store more data
on a single queue.
When Should the Value of This Tunable Be Lowered?
Lower this tunable when applications have no need to store large amounts
of data on a single queue.
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
msgmnb,
msgmni,
msgmbs,
and
msgtql.
Specifically, when the
msgmnb
tunable is changed, adjustments may also be needed to the
msgmbs
and
msgtql
tunables.
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
msgmnb
was developed by AT&T.
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