VSAM RLS uses share and exclusive record locks to control access to the shared data. An exclusive lock is used to ensure that a single user is updating a specific record. The exclusive lock causes any read-with-integrity request for the record by another user (CICS transaction or non-CICS application) to wait until the update is finished and the lock released.

Failure conditions can delay completion of an update to a recoverable data set. This occurs when a CICS transaction enters in-doubt status. This means CICS can neither rollback nor commit the transaction. Therefore, the recoverable records modified by the transaction must remain locked. Failure of a CICS AOR also causes the current transaction's updates to recoverable data sets not to complete. They cannot complete until the AOR is restarted.

When a transaction enters in-doubt, sysplex failure, MVS failure, failure of an instance of the SMSVSAM Address Space, or a CICS AOR terminates, any exclusive locks on records of recoverable data sets held by the transaction must remain held. However, other users waiting for these locks should not continue to wait. The outage is likely to be longer than the user would want to wait. When these conditions occur, VSAM RLS converts these exclusive record locks into retained locks.

Both exclusive and retained locks are not available to other users. When another user encounters lock contention with an exclusive lock, the user's lock request waits. When another user encounters lock contention with a retained lock, the lock request is immediately rejected with “retained lock” error response. This results in the VSAM record management request that produced the lock request failing with “retained lock” error response.

If you close a data set in the middle of a transaction or unit of recovery and it is the last close for this data set on this system, then RLS converts the locks from active to retained.