unit of recovery, resolving in-doubt units of recovery, IMS" /> How in-doubt units of recovery are resolved from IMS

 

How in-doubt units of recovery are resolved from IMS

Resolving in-doubt units of recovery in IMS has no effect on DL/I resources. IMS is in control of recovery coordination and, when it restarts, automatically commits or backs out incomplete DL/I work. The decision to commit or back out for online regions (non-fast-path) is on the presence or absence of IMS log record types X'3730' and X'3801' respectively. The existence of in-doubt units of recovery does not imply that DL/I records are locked until WebSphere MQ connects.

During queue manager restart, WebSphere MQ makes a list of in-doubt units of recovery. IMS builds its own list of residual recovery entries (RREs). The RREs are logged at IMS checkpoints until all entries are resolved.

During reconnection of an IMS region to WebSphere MQ, IMS indicates to WebSphere MQ whether to commit or back out units of work marked in WebSphere MQ as in doubt.

When in-doubt units are resolved:

  1. If WebSphere MQ recognizes that it has marked an entry for commit and IMS has marked it to be backed out, WebSphere MQ issues message CSQQ010E. WebSphere MQ issues this message for all inconsistencies of this type between WebSphere MQ and IMS.

  2. If WebSphere MQ has any remaining in-doubt units, the adapter issues message CSQQ008I.

For all resolved units, WebSphere MQ updates queues as necessary and releases the corresponding locks.

WebSphere MQ maintains locks on in-doubt work that was not resolved. This can cause a backlog in the system if important locks are being held. The connection remains active so we can resolve the IMS RREs. Recover the in-doubt threads by the methods described in the WebSphere MQ for z/OS System Administration Guide.

All in-doubt work should be resolved unless there are software or operating problems, such as with an IMS cold start. In-doubt resolution by the IMS control region takes place in two circumstances:

  1. At the start of the connection to WebSphere MQ, during which resolution is done synchronously.

  2. When a program abends, during which the resolution is done asynchronously.