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Use the TCP listener backlog option

 

When receiving on TCP, a maximum number of outstanding connection requests is set. This can be considered a backlog of requests waiting on the TCP port for the listener to accept the request.

The default listener backlog value on i5/OS is 255. If the backlog reaches this value, the TCP connection is rejected and the channel will not be TCP: able to start.

For MCA channels, this results in the channel going into a RETRY state and retrying the connection at a later time.

For client connections, the client receives an MQRC_Q_MGR_NOT_AVAILABLE reason code from MQCONN and should retry the connection at a later time.

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

ListenerBacklog = n

This overrides the default maximum number of outstanding requests (255) for the TCP listener.

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

 

Parent topic:

Receiving on TCP

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