IBM SC34-7012-01 manual Recovery for extrapartition transient data, Input extrapartition data sets

Recovery for extrapartition transient data

CICS does not recover extrapartition data sets. If you depend on extrapartition data, you will need to develop procedures to recover data for continued execution on restart following either a controlled or an uncontrolled shutdown of CICS.

There are two areas to consider in recovering extrapartition data sets:

vInput extrapartition data sets

vOutput extrapartition data sets

Input extrapartition data sets

The main information required on restart is the number of records processed up to the time the system ended. This can be recorded during processing, using CICS journaling, as described in the following paragraphs.

Each application program that reads records from extrapartition input queues should first enqueue exclusive access to those queues. This prevents interleaved access to the same queues by other concurrently executing tasks.

The application programs then issue READQ TD commands to read and process extrapartition input records. In this way, they accumulate the total of input records read and processed during execution for each queue. The total number of READQ operations is written to a journal data set, together with the relevant destination identifications. This journaling should be done immediately before RETURN or SYNCPOINT commands.

Following output of the journal record, each application program dequeues itself from the extrapartition input queues to permit other application programs to access those queues.

If uncontrolled shutdown occurs before this journaling, no records will appear on the journal data set for that unit of work. The effect of that in-flight task is, therefore, automatically backed out on emergency restart. However, if the journal record is written before uncontrolled shutdown, this completed input data set processing will be recognized on emergency restart.

On emergency restart following uncontrolled shutdown or on a warm start following a controlled shutdown, use the following procedure, which will reposition the extrapartition input data sets to reflect the input and processing of their records during previous CICS operation.

You can identify an extrapartition input recovery program in the PLT for execution during the initialization phase. This program reads the journal data set forward. Each journaled record indicates the number of READQ operations performed on the relevant extrapartition input data set during previous execution of application programs. The same number of READQ TD commands is issued again by the recovery program, to the same input queue that was referenced previously.

On reaching the end of the journal data set, the extrapartition input data sets are positioned at the same point they had reached before the initiation of tasks that were in-flight at uncontrolled shutdown. The result is the logical recovery of these input data sets with in-flight task activity backed out.

134CICS TS for z/OS 4.1: Recovery and Restart Guide