vWorking storage

vAny LU6.2 sessions

vAny LU6.1 links

vAny MRO links

The resources CICS retains include:

vLocks on recoverable data. If the unit of work is shunted indoubt, all locks are retained. If it is shunted because of a commit- or backout-failure, only the locks on the failed resources are retained.

vSystem log records, which include:

Records written by the resource managers, which they need to perform recovery in the event of transaction or CICS failures. Generally, these records are used to support transaction backout, but the RDO resource manager also writes records for rebuilding the CICS state in the event of a CICS failure.

CICS recovery manager records, which include identifiers relating to the original transaction such as:

-The transaction ID

-The task ID

-The CICS terminal ID

-The VTAM LUNAME

-The user ID

-The operator ID.

Locks

For files opened in RLS mode, VSAM maintains a single central lock structure using the lock-assist mechanism of the MVS coupling facility. This central lock structure provides sysplex-wide locking at a record level. Control interval (CI) locking is not used.

The locks for files accessed in non-RLS mode, the scope of which is limited to a single CICS region, are file-control managed locks. Initially, when CICS processes a read-for-update request, CICS obtains a CI lock. File control then issues an ENQ request to the enqueue domain to acquire a CICS lock on the specific record. This enables file control to notify VSAM to release the CI lock before returning control to the application program. Releasing the CI lock minimizes the potential for deadlocks to occur.

For coupling facility data tables updated under the locking model, the coupling facility data table server stores the lock with its record in the CFDT. As in the case of RLS locks, storing the lock with its record in the coupling facility list structure that holds the coupling facility data table ensures sysplex-wide locking at record level.

For both RLS and non-RLS recoverable files, CICS releases all locks on completion of a unit of work. For recoverable coupling facility data tables, the locks are released on completion of a unit of work by the CFDT server.

Active and retained states for locks

CICS supports active and retained states for locks.

14CICS TS for z/OS 4.1: Recovery and Restart Guide

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IBM SC34-7012-01 manual Locks, Active and retained states for locks