Default transmission queue restriction

The product documentation in versions of IBM® WebSphere® MQ before Version 7.1 warned about defining the default transmission queue as SYSTEM.CLUSTER.TRANSMIT.QUEUE, but no error was reported. In Version 7.1, any attempt to set or use a default transmission queue that is defined as SYSTEM.CLUSTER.TRANSMIT.QUEUE results in an error.

In versions of IBM WebSphere MQ before Version 7.1, no error was reported when defining the default transmission queue as SYSTEM.CLUSTER.TRANSMIT.QUEUE. MQOPEN or MQPUT1 MQI calls that resulted in referencing the default transmission queue did not return an error. Applications might have continued working and failed later on. The reason for the failure was hard to diagnose.

The change from Version 7.1 onwards ensures that any attempt to set the default transmission queue to SYSTEM.CLUSTER.TRANSMIT.QUEUE, or use a default transmission queue set to SYSTEM.CLUSTER.TRANSMIT.QUEUE, is immediately reported as an AMQ8520 error.