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Full Discussion: Unix message Queue
Top Forums UNIX for Advanced & Expert Users Unix message Queue Post 38909 by kel on Wednesday 30th of July 2003 08:42:51 AM
Old 07-30-2003
Hi,
Thanks for your replay.

I'll try to be more clear -
1. i have created the Q as follow:
'o_qid = msgget(IPC_PRIVATE,IPC_CREAT|0777|IPC_EXCL|S_IRUSR|S_IWUSR);'

And worked with the Q as follow:
'msgsnd( qid, (void*)(&eventDataBuffer), MessageSize, 0) '
'qbytesread=msgrcv(qid, (void*)pMessage, max_msgsize, -MSGTYPE_MAX_APP_RANGE, 0)'

2. The Q has functioned OK for about an hour, where data was surely sent & received.

3. On a certain point, i could not send, nor receive from the Q.
The parameters on the Q where:
Qnum=0 (The number of messages currently outstanding on the
associated message queue.)
CBYTES= ~4k (The number of bytes in messages currently outstanding on the associated message queue.)

This is what i do not understand. How come there are no messages, and the Q inform me that the data size is greater than 0?

I hope i made more clear.
Thanks Again.
 

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msgmni(5)							File Formats Manual							 msgmni(5)

NAME
msgmni - maximum number of system-wide System V IPC message queues (IDs) allowed VALUES
Default Failsafe Allowed Values DESCRIPTION
The 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 identifiers. Applications use the system call to create new queues. If all IDs have been used, will return 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 command. Message queue status can be monitored using the command. For more information about System V message queues, refer to the 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 What Other Tunable Values Should Be Changed at the Same Time? All the System V message queue tunables are interrelated and should 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 and Specifically, and tunables may need adjustment along with changes to the 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 tun- able values, consult the documentation for the kernel software being installed. For information about optional kernel software that was factory installed on your system, see at AUTHOR
was developed by AT&T. SEE ALSO
ipcrm(1), ipcs(1), msgget(2), mesg(5), msgmnb(5), msgtql(5), msgmbs(5). Tunable Kernel Parameters msgmni(5)
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