Design overview

In the creation of the program control table (PCT), the system programmer can designate selected transactions as restartable.

During the execution of any transaction, certain temporary-storage data, intrapartition destinations, and files are protected for dynamic backout. In addition, for a restartable transaction, the following actions take place:

If a transaction abends, but before backout has been attempted, DFHREST may be invoked to decide whether or not the task is to be restarted. Even if DFHREST decides that the transaction can be restarted, CICS® may overrule the restart, for example because of a transaction backout failure.

DFHREST is invoked by DFHXMTA passing a parameter list via a COMMAREA that is mapped by the DFHXMRSD DSECT. DFHREST should return to DFHXMTA, indicating whether or not the transaction should be restarted. If DFHREST requests a restart, and CICS does not overrule this decision, the principal facility is not released and the principal facility owner reattaches a new task to restart the transaction.

Notes:
  1. DFHREST can invoke CICS facilities such as file control and transient data, via the command-level interface.
  2. If an error occurs while linking to, or in, the transaction restart program, the restart is not attempted for this task.
  3. DFHREST runs before backout.
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