clapper@nadc.arpa (10/22/87)
We're running System V Release 2.0 on a VAX 11/780, and we've encountered some intermittent problems with message queues. On several occasions, the "msg_qbytes" field of a queue was set to its maximum value of 65535. I understand only superuser can modify that queue parameter, and none of our application software using queues runs as superuser. In another case, attempts to enqueue messages began to fail, returning an errno of 11 (EAGAIN). According to msgop(2), this error means either the message queue is full, or the total number of messages on all queues equals the max. allowed value. Ipcs(1) showed all queues to be empty, although that that obviously doesn't prove anything since the problem is time-dependent. As far as the system-wide limit goes, our /etc/master file has the following message-related parameters: MSGMAP 100 MSGMAX 8192 MSGMNB 16384 MSGMNI 50 MSGSSZ 8 MSGTQL 40 MSGSEG 1024 I understand that MSGTQL is the maximum number of outstanding messages on all queues. Despite the apparent limit of 40, I was able with a test program to place 201 messages on a queue before the enqueue operation failed. I've found no mention of a queue-related problem with these symptoms in the AT&T UNIX System V Known Problem List of July 1987. Has anyone else run into this kind of problem? Could this be an unreported operating system bug? Or, have we made some unwitting error configuring our system? Please send any replies to me personally, as I do not receive the digest on a regular basis. Thanks in advance. Brian M. Clapper ARPA: clapper@nadc.arpa Code 7031 Naval Air Development Center Street and Jacksonville Roads Warminster, PA 18974 (215) 441-2118