How consistency is maintained

If data in WebSphere MQ is to be consistent with batch, CICS, IMS, or TSO, any data changed in one must be matched by a change in the other. Before one system commits the changed data, it must know that the other system can make the corresponding change. So, the systems must communicate.

During a two-phase commit (for example under CICS), one subsystem coordinates the process. That subsystem is called the coordinator; the other is the participant. CICS or IMS is always the coordinator in interactions with WebSphere MQ, and WebSphere MQ is always the participant. In the batch or TSO environment, WebSphere MQ can participate in two-phase commit protocols coordinated by z/OS RRS.

During a single-phase commit (for example under TSO or batch), WebSphere MQ is always the coordinator in the interactions and completely controls the commit process.

In a WebSphere Application Server environment, the semantics of the JMS session object determine whether single-phase or two-phase commit coordination is used.