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1. CICS invokes DFHREST only when RESTART(YES) is specified in a
transaction’s resource definition.
2. Ensure that resources used by restartable transactions, such as files, temporary
storage, and intrapartition transient data queues, are defined as recoverable.
3. When transaction restart occurs, a new task is attached that invokes the initial
program of the transaction. This is true even if the task abended in the second
or subsequent unit of work, and DFHREST requested a restart.
4. CICS keeps statistics on the total number of restarts against each transaction.
5. Emergency restart does not restart any user tasks that were in-flight when CICS
abnormally terminated. Instead, recovery manager attaches a special task for
each in-flight task that had recovery records in the system log at abnormal
termination. This task invokes each resource manager to backout recoverable
resources.
6. Making a transaction restartable can involve slightly more overhead, because
copies of the TCTUA, COMMAREA, and terminal input/output area (TIOA)
have to be kept in case the transaction needs to be restarted. For more
information about making transactions restartable, see the CICS Customization
Guide.
7. In some cases, the benefits of transaction restart can be obtained instead by
using the SYNCPOINT ROLLBACK command. See the CICS Distributed Transaction
Programming Guide for information about using this command in an MRO
environment.
8. A transaction initiated by terminal input is allowed to restart during shutdown,
even if the transaction is defined as SHUTDOWN(DISABLED).
Actions taken at transaction failure
The CICS transaction failure program (TFP) is invoked during abnormal
transaction termination, unless the transaction is to be restarted.
The TFP is invoked when the following conditions apply:
v There is a failure during execution and before syncpoint processing has begun.
v There is a failure during syncpoint processing.
The principal action of the transaction failure program is to send, if possible, an
abend message to the terminal connected to the abending transaction. It also sends
a message to the CSMT transient data queue.
Except for transaction failures that occur during syncpoint processing, and before
sending the message to the CSMT queue, the transaction failure program links to
the user-replaceable program error program, DFHPEP. The CICS transaction failure
program gives control to DFHPEP through a LINK. This LINK occurs after all
program-level abend exit code has been executed by the task that abnormally
terminates, but before dynamic transaction backout (if any) has been performed.
Processing operating system abends and program checks
There is a limit to the processing you can attempt after an operating system abend
or a program check.
If the program check or abend is associated with any domain other than the
application domain, you have no further part in processing the error. If the
program check or abend is in the application domain, one of the following can
occur:
94 CICS TS for z/OS 4.1: Recovery and Restart Guide