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Chapter 8. Unit of work recovery and abend processing
A number of different events can cause the abnormal termination of transactions in
CICS.
These events include:
v A transaction ABEND request issued by a CICS management module.
v A program check or operating system abend (this is trapped by CICS and
converted into an ASRA or ASRB transaction abend).
v An ABEND request issued by a user application program.
v A CEMT, or EXEC CICS, command such as SET TASK PURGE or FORCEPURGE.
Note: Unlike the EXEC CICS ABEND command above, these EXEC CICS
commands cause other tasks to abend, not the one issuing the command.
v A transaction abend request issued by DFHZNEP or DFHTEP following a
communication error. This includes the abnormal termination of a remote CICS
during processing of in-flight distributed UOWs on the local CICS.
v An abnormal termination of CICS, in which all in-flight transactions are
effectively abended as a result of the CICS region failing.
In-flight transactions are recovered during a subsequent emergency restart to
enable CICS to complete the necessary backout of recoverable resources, which
is performed in the same way as if the task abended while CICS was running.
Unit of work recovery
A unit of work in CICS is also the unit of recovery - that is, it is the atomic
component of the transaction in which any changes made either must all be
committed, or must all be backed out.
A transaction can be composed of a single unit of work or multiple units of work.
In CICS, recovery is managed at the unit of work level.
For recovery purposes, CICS recovery manager is concerned only with the units of
work that have not yet completed a syncpoint because of some failure. This topic
discusses how CICS handles these failed units of work.
The CICS recovery manager has to manage the recovery of the following types of
unit of work failure:
In-flight-failed
The transaction fails before the current unit of work reaches a syncpoint, as
a result either of a task abend, or the abnormal termination of CICS. The
transaction is abnormally terminated, and recovery manager initiates
backout of any changes made by the unit of work.
See “Transaction backout” on page 74.
Commit-failed
A unit of work fails during commit processing while taking a syncpoint. A
partial copy of the unit of work is shunted to await retry of the commit
process when the problem is resolved.
This does not cause the transaction to terminate abnormally.
© Copyright IBM Corp. 1982, 2010 73