How in-doubt units of recovery are resolved from CICS
The resolution of in-doubt units has no effect on CICS resources. CICS is in control of recovery coordination and, when it restarts, automatically commits or backs out each unit, depending on whether there was a log record marking the beginning of the commit. The existence of in-doubt objects does not lock CICS resources while WebSphere MQ is being reconnected.
One of the functions of the CICS adapter is to keep data synchronized between CICS and WebSphere MQ. If a queue manager abends while connected to CICS, it is possible for CICS to commit or back out work without WebSphere MQ being aware of it. When the queue manager restarts, that work is termed in doubt.
WebSphere MQ cannot resolve these in-doubt units of recovery (that is, commit or back out the changes made to WebSphere MQ resources) until the connection to CICS is restarted or reconnected.
A process to resolve in-doubt units of recovery is initiated during startup of the CICS adapter. The process starts when the adapter requests a list of in-doubt units of recovery. Then:
- The adapter receives a list of in-doubt units of recovery for this connection ID from WebSphere MQ, and passes them to CICS for resolution.
- CICS compares entries from this list with entries in its own log. CICS determines from its own list what action it took for each in-doubt unit of recovery.
Under some circumstances, CICS cannot run the WebSphere MQ process to resolve in-doubt units of recovery. When this happens, WebSphere MQ sends one of the following messages:
- CSQC404E
- CSQC405E
- CSQC406E
- CSQC407E
followed by the message CSQC408I.
For details of what these messages mean, see the WebSphere MQ for z/OS Messages and Codes manual.
For all resolved units, WebSphere MQ updates the queues as necessary and releases the corresponding locks. Unresolved units can remain after restart. Resolve them by the methods described in the WebSphere MQ for z/OS System Administration Guide.