CICS failure

If CICS® fails, DBCTL retains locks on database records updated by indoubt UOWs. These records remain unavailable until in-doubts are resolved. CICS records information about the disposition of UOWs on its log.

A CICS warm start or emergency restart reconstructs information describing UOWs that may be indoubt. When CICS reconnects to DBCTL, DBCTL returns a list of any indoubt UOWs. CICS notifies DBCTL of the resolution of all in-doubts, so DBCTL can commit or backout as appropriate.

If CICS fails, or if you need to cause an immediate shutdown, CICS attempts to disconnect from DBCTL. At this time, CICS gives the requests in progress time to complete before shutdown occurs. The time is specified in the DRA startup table parameter, TIMEOUT. (For information on this parameter, see Defining the IMS DRA startup parameter table.) If TIMEOUT is exceeded and CICS terminates while threads are still active in DBCTL, a U113 abend of DBCTL will occur. If this happens, you will have to restart DBCTL (IMS).

Choosing a value for TIMEOUT involves a trade-off between the length of restart process, which might be delayed if the value you specify is too high, and the risk of causing U113 abends, which might increase if you specify to low a value. One possible solution is to specify a TIMEOUT value that is about equal to the average length of time between BMP checkpoints. If a BMP checkpoint has been taken, there is less likelihood that CICS resources are waiting. This lessens the likelihood of U113 abends without lengthening the restart process too much.

If you want an abnormal termination of CICS and CICS does not respond to an immediate shutdown, use an MVS CANCEL command. This command, and CICS abends with different causes, should not result in an IMS U113 abend because DBCTL traps the CANCEL and an MVS system abend code of 08E is issued instead. Changing the effect of an MVS CANCEL from a U113 abend to an MVS system abend of 08E makes the effects of a CANCEL more like the effects of a CICS immediate shutdown. If you have been obliged to cancel CICS in this way, do not start CICS with the START=INITIAL system initialization parameter unless absolutely necessary, especially if there is a possibility of indoubt units of work for DBCTL, because CICS will lose its record of the indoubt units of work.

For further information on the effects of a CICS failure in a DBCTL environment, see the section on CCTL termination in the appropriate Exit routines in IMS product documentation.