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Use the SPX listener backlog option

 

When receiving on SPX, a maximum number of outstanding connection requests is set. This can be considered a backlog of requests waiting on the SPX port for the listener to accept the request. The default listener backlog values are shown in Table 1.

Default outstanding connection requests on Windows

Platform	Default listener backlog value
Windows Server	5
Windows Workstation	5

If the backlog reaches the values in Table 1, the reason code, MQRC_Q_MGR_NOT_AVAILABLE is received when trying to connect to the queue manager using MQCONN or MQCONNX. If this happens, it is possible to try to connect again.

However, to avoid this error, we can add an entry in the qm.ini file or in the registry for Windows:

SPX:
ListenerBacklog = n

This overrides the default maximum number of outstanding requests (see Table 1) for the SPX listener.

Some operating systems support a larger value than the default. If necessary, this can be used to avoid reaching the connection limit.

To run the listener with the backlog option switched on either:

• Use the RUNMQLSR -b command, or

• Use the MQSC command DEFINE LISTENER with the BACKLOG attribute set to the desired value.

For information about the RUNMQLSR command, see the WebSphere MQ System Administration Guide book. For information about the DEFINE LISTENER command, see the Websphere MQ Script (MQSC) Command Reference.

 

Parent topic:

Receiving on SPX

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