1. MQ Cross Process Transaction Tracing (CPTT) is enabled with MQAgent.properties property "mq.crossprocesstracing.enabled=true".
The CPTT feature requires the Activity Recording feature of WebSphere MQ to be enabled. With that feature the Queue Manager (QM) allows the generation of queue activity messages into the SYSTEM.ADMIN.ACTIVITY.QUEUE which are then polled for by the MQMonitor agent configured for that QM.
The additional factor controlling when activity messages are generated is that only when CPTT is enabled does the MQ Agent set the activity bit in any MQ messages created by the monitored MQ Java Connector application, which in turn results in the activity message generation.
2. The handshaking was built as an additional safety mechanism to avoid the possibility of activity messages overflowing from an activity queue into the Dead Letter Queue (DLQ) because they were not being polled by a MQMonitor Agent. Normally it is not desirable to mix business and system messages in the DLQ.
By enabling handshake, activity messages are only generated in the QM if that QM's MQMonitor agent ID is contained in the handshake list. As the activity messages are not going to be generated in the QM which is not being monitored by an MQMonitor agent, this avoids unnecessary generation of messages in any QM activity queue that is not being monitored.