IBM SC34-7012-01 Defining log streams to MVS, Defining system log streams, System log streams

System log streams

These are used by the CICS log manager and the CICS recovery manager exclusively for unit of work recovery purposes. Each system log is unique to a CICS region, and must not be merged with any other system log.

General log streams

These are used by the CICS log manager for all other types of logging and journaling. You can merge forward recovery records, autojournal records, and user journal records onto the same general log stream, from the same, or from different, CICS regions.

For information on how CICS handles the different error conditions detected by the CICS log manager, see the CICS Problem Determination Guide.

Defining log streams to MVS

Log streams are MVS resources that reside in the coupling facility (if one is used), and in data sets.

About this task

All log streams required by CICS must be defined to the MVS system logger before CICS can use them. You can either define log streams explicitly, or you can let CICS create them dynamically when they are first used. To enable CICS to create log streams dynamically, you first define model log streams to the MVS system logger. To define explicit log streams and model log streams, use the MVS IXCMIAPU utility.

For information about defining coupling facility log streams and DASD-only log streams, see the CICS Transaction Server for z/OS Installation Guide. For more information about the coupling facility and defining log structures generally, see z/OS MVS Setting Up a Sysplex.

Defining system log streams

You must define a system log if you want to preserve data integrity in the event of unit of work failures and CICS failures .

About this task

A system log is mandatory for the following processes:

vThe backout of recoverable resources changed by failed units of work

vCold starts, to enable CICS to restore units of work that were shunted at the time of the shutdown

vWarm restarts, to enable CICS to restore the region to its state at the previous shutdown, including units of work that were shunted at the time of the shutdown

vEmergency restarts, to enable CICS to:

–Restore the region to its state at the previous shutdown, including units of work that were shunted at the time of the shutdown

–Recover units of work that were in-flight at the time of the CICS failure, and perform backout of recoverable resources that were updated before the failure

108CICS TS for z/OS 4.1: Recovery and Restart Guide