IBM SC34-7012-01 Shutdown initiated by CICS log manager, Effect of problems with the system log

If you ever need to redefine and reinitialize the CICS local catalog, you should also reinitialize the global catalog. After reinitializing both catalog data sets, you must perform an initial start.

Shutdown initiated by CICS log manager

The CICS log manager initiates a shutdown of the region if it encounters an error in the system log that indicates previously logged data has been lost.

In addition to initiating the shutdown, the log manager informs the recovery manager of the failure, which causes the recovery manager to set the type-of-restart indicator to “no-restart-possible” and to issue message DFHRM0144. The result is that recovery during a subsequent restart is not possible and you can perform only an initial start of the region. To do this you are recommended to run the recovery manager utility program (DFHRMUTL) to force an initial start, using the SET_AUTO_START=AUTOINIT option.

During shutdown processing, existing transactions are given the chance to complete their processing. However, no further data is written to the system log. This strategy ensures that the minimum number of units of work are impacted by the failure of the system log. This is because:

vIf a unit of work does not attempt to backout its resource updates, and completes successfully, it is unaffected by the failure.

vIf a unit of work does attempt to backout, it cannot rely on the necessary log records being available, and therefore it is permanently suspended.

Therefore, when the system has completed the log manager-initiated shutdown all (or most) units of work will have completed normally during this period and if there are no backout attempts, data integrity is not compromised.

Effect of problems with the system log

A key value of CICS is its ability to implement its transactional recovery commitments and thus safeguard the integrity of recoverable data updated by CICS applications.

This ability relies upon logging before-images and other information to the system log. However, the system log itself might suffer software or hardware related problems, including failures in the CICS recovery manager, the CICS logger domain, or the MVS system logger. Although problems with these components are unlikely, you must understand the actions to take to minimize the impact of such problems.

If the CICS log manager detects an error in the system log that indicates previously logged data has been lost, it initiates a shutdown of the region. This action minimizes the number of transactions that fail after a problem with the log is detected and therefore minimizes the data integrity exposure.

Any problem with the system log that indicates that it might not be able to access all the data previously logged invalidates the log. In this case, you can perform only a diagnostic run or an initial start of the region to which the system log belongs.

The reason that a system log is completely invalidated by these kinds of error is that CICS can no longer rely on the data it previously logged being available for recovery processing. For example, the last records logged might be unavailable,

Chapter 3. Shutdown and restart recovery 33