IBM SC34-7012-01 manual Lost locks recovery, Rebuilding the lock structure, About this task

CICS recovers after a cache failure automatically. There is no need for manual intervention (other than the prerequisite action of resolving the underlying cause of the cache failure).

Lost locks recovery

The failure of a coupling facility lock structure that cannot be rebuilt by VSAM creates the lost locks condition.

The lost locks condition can occur only for data sets opened in RLS mode. A data set can be made available for general use only after all the CICS regions that were accessing the data set at the time of the lock structure failure have completed the process known as lost locks recovery.

Issue the IDCAMS SHCDS LISTUBSYS(ALL) command to display the lost locks and the owners of those locks.

Rebuilding the lock structure

When a coupling facility lock structure fails, the SMSVSAM servers attempt to rebuild their locks in the lock structure from their own locally-held copies of the locks. If this is successful, the failure is transparent to CICS.

About this task

If the rebuild fails, all SMSVSAM servers abend and restart, but they are not available for service until they can successfully connect to a new coupling facility lock structure. Thus a lock structure failure is initially detected by CICS as an SMSVSAM server failure, and CICS issues message DFHFC0153.

When the SMSVSAM servers abend because of this failure, the sharing control data set is updated to reflect the lost locks condition. The sharing control data set records:

vThe data sets whose locks have been lost.

vThe CICS regions that must complete lost locks recovery for each data set. These are the CICS regions that had a data set open for update (in RLS-mode) for which the locks have been lost.

Notifying CICS of SMSVSAM restart

When the SMSVSAM servers are able to connect to a new lock structure, they use the MVS ENF to notify the CICS regions that their SMSVSAM server is available again.

CICS is informed during dynamic RLS restart about those data sets for which it must perform lost locks recovery. CICS issues a message (DFHFC0555) to inform you that lost locks recovery is to be performed for one or more data sets.

If a lost-locks condition occurs and is not resolved when a CICS restart (warm or emergency) occurs, CICS is notified during file control restart about any data sets for which it must perform lost locks recovery. On a cold start, CICS does not perform any lost locks recovery, and the information in the sharing control data set, which records that CICS must complete lost locks recovery, is cleared for each data set. This does not affect the information recorded for other CICS regions.

Only units of work performing lost locks recovery can use data sets affected by lost locks. Error responses are returned on open requests issued by any CICS

Chapter 8. Unit of work recovery and abend processing 89