Tunable Kernel Parameters
NAME [Toc] [Back]
msgmnb - maximum number of bytes on a single System V IPC message
VALUES [Toc] [Back]
Failsafe [Toc] [Back]
Allowed Values [Toc] [Back]
Maximum: 64*1024*1024 or (msgssz*msgseg), whichever is smaller.
DESCRIPTION [Toc] [Back]
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?
Restrictions on Changing [Toc] [Back]
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
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 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.
Hewlett-Packard Company - 1 - HP-UX 11i Version 2: Sep 2004
Tunable Kernel Parameters
WARNINGS [Toc] [Back]
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
AUTHOR [Toc] [Back]
msgmnb was developed by AT&T.
SEE ALSO [Toc] [Back]
msgrcv(2), msgsnd(2), mesg(5), msgmap(5), msgmax(5), msgmni(5),
msgseg(5), msgssz(5), msgtql(5).
Hewlett-Packard Company - 2 - HP-UX 11i Version 2: Sep 2004 [ Back ]