What happens during an immediate shutdown (PERFORM SHUTDOWN IMMEDIATE)

During immediate shutdown of CICS®, possibly requested by the main terminal operator or an application program, processing is different from a normal shutdown in the following important ways.

  • User tasks are not guaranteed to complete for any kind of shutdown. They are just given less time for immediate shutdown before being purged.
  • None of the programs listed in the shutdown PLT are run.
  • CICS does not write a warm keypoint or a warm-start-possible indicator to the global catalog.
  • CICS does not close files defined to CICS file control.

To preserve data integrity, the next initialization of CICS must be an emergency restart. If the next initialization of CICS specifies START=AUTO, there will be an emergency restart.

The processing involved in immediate shutdown is described as CICS system termination processing. (In comparison, normal shutdown involves quiesce processing.)

Unlike processing, controls are not exercised to ensure that resources and services remain available as long as they are needed. One consequence of this is that transaction and CICS system abends can occur during immediate shutdown. Thus, if a task tries to use a resource that has already been terminated, the task abends. Then dynamic transaction backout is invoked, and that might also fail because it could also try to use a resource that has been terminated.

In addition, if CICS system termination processing is delayed significantly, tasks in the system waiting for input from terminals that are no longer available are likely to extend beyond the period for deadlock timeout specified in the DTIMOUT option of the TRANSACTION definition.

First stage of immediate shutdown

During the first stage of an immediate shutdown, the following processes take place:
  1. WLMHEALTH is set to IMMCLOSED, and thereby the z/OS® WLM health value is set to 0.
  2. 6.2 and later For a CMAS, CICS processes the CMAS shutdown. For a MAS, CICS stops the MAS agent code. For a WUI server region started with CPSMCONN=WUI, CICS processes the WUI shutdown.
  3. The system termination task drives the collection of termination statistics.
  4. If there is a terminal associated with the event that caused the immediate shutdown, a message is sent to inform the operator that CICS is terminating.
  5. If the shutdown request has arrived by transaction routing, the associated terminal is freed.
  6. Terminal input is no longer accepted.
  7. The Front End Programming Interface (FEPI) is requested to shut down immediately. Unless SDTRAN=NO or NOSDTRAN was specified, the shutdown task starts the specified shutdown transaction (the default is CESD). CESD manages the purging of long-running user tasks.

Second stage of immediate shutdown

During the second stage of an immediate shutdown, the following processing takes place:
  1. Transient data is terminated.
  2. A dump is taken, if requested.
  3. Interregion sessions are terminated.
  4. If CICS is signed on to the CICS availability manager (CAVM), a signoff abnormal request is made from CAVM.
  5. The local catalog and global catalog are left to be closed by the operating system.
  6. The following message is issued: 
    DFHKE1799 applid TERMINATION OF CICS IS COMPLETE
  7. CICS completes some internal processing, then returns control to z/OS.