IBM SC34-7012-01 Shutdown and restart recovery, Normal shutdown processing, First quiesce stage

Chapter 3. Shutdown and restart recovery

CICS can shut down normally or abnormally and this affects the way that CICS restarts after it shuts down.

CICS can stop executing as a result of:

vA normal (warm) shutdown initiated by a CEMT, or EXEC CICS, PERFORM SHUT command

vAn immediate shutdown initiated by a CEMT, or EXEC CICS, PERFORM SHUT IMMEDIATE command

vAn abnormal shutdown caused by a CICS system module encountering an irrecoverable error

vAn abnormal shutdown initiated by a request from the operating system (arising, for example, from a program check or system abend)

vA machine check or power failure

Normal shutdown processing

Normal shutdown is initiated by issuing a CEMT PERFORM SHUTDOWN command, or by an application program issuing an EXEC CICS PERFORM SHUTDOWN command. It takes place in three quiesce stages, as follows:

First quiesce stage

During the first quiesce stage of shutdown, all terminals are active, all CICS facilities are available, and the a number of activities are performed concurrently

The following activities are performed:

vCICS invokes the shutdown assist transaction specified on the SDTRAN system initialization parameter or on the shutdown command.

Because all user tasks must terminate during the first quiesce stage, it is possible that shutdown could be unacceptably delayed by long-running tasks (such as conversational transactions). The purpose of the shutdown assist transaction is to allow as many tasks as possible to commit or back out cleanly, while ensuring that shutdown completes within a reasonable time.

CICS obtains the name of the shutdown assist transaction as follows:

1.If SDTRAN(tranid) is specified on the PERFORM SHUTDOWN command, or as a system initialization parameter, CICS invokes that tranid.

2.If NOSDTRAN is specified on the PERFORM SHUTDOWN command, or as a system initialization parameter, CICS does not start a shutdown transaction. Without a shutdown assist transaction, all tasks that are already running are allowed to complete.

3.If the SDTRAN (or NOSDTRAN) options are omitted from the PERFORM SHUTDOWN command, and omitted from the system initialization parameters, CICS invokes the default shutdown assist transaction, CESD, which runs the CICS-supplied program DFHCESD.

The SDTRAN option specified on the PERFORM SHUT command overrides any SDTRAN option specified as a system initialization parameter.

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