NAME
msgmnb — maximum number of bytes on a single System V IPC message queue
VALUES
Allowed Values
Minimum: 0
Maximum: 64*1024*1024
or
(msgssz*msgseg),
whichever is smaller.
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
None. 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
mesg
tunables include
msgmap,
msgmax,
msgmnb,
msgmni,
msgseg,
msgssz,
and
msgtql.
Specifically, when the
msgmnb
tunable is changed, adjustments may also be needed to the
msgseg
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.
AUTHOR
msgmnb
was developed by AT&T.
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