Syncpoints in IMS applications

 

In an IMS application, establish a syncpoint by using IMS calls such as GU (get unique) to the IOPCB and CHKP (checkpoint). To back out all changes since the previous checkpoint, we can use the IMS ROLB (rollback) call. For more information, see the following books:

The queue manager (in conjunction with the IMS syncpoint manager) participates in a two-phase commit protocol if other recoverable resources are also involved in the unit of work.

All open handles are closed by the IMS adapter at a syncpoint (except in a nonmessage batch-oriented BMP). This is because a different user could initiate the next unit of work and WebSphere MQ security checking is performed when the MQCONN, MQCONNX, and MQOPEN calls are made, not when the MQPUT or MQGET calls are made. The handles are closed at the beginning of the MQI call following the IMS™ call which initiated the syncpoint.

If you have not installed IMS APAR PN83757, handles are also closed after a ROLB call unless you are running IMS V3 or are running a nonmessage BMP.

If an IMS application (either a BMP or an MPP) issues the MQDISC call, open queues are closed but no implicit syncpoint is taken. If the application closes down normally, any open queues are closed and an implicit commit occurs. If the application closes down abnormally, any open queues are closed and an implicit backout occurs.

 

Parent topic:

Syncpoints in WebSphere MQ for z/OS applications


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