IBM SC34-7012-01 manual System activity keypoints, Forward recovery logs

CICS also writes “backout-failed” records to the system log if a failure occurs in backout processing of a VSAM data set during dynamic backout or emergency restart backout.

Records on the system log are used for cold, warm, and emergency restarts of a CICS region. The only type of start for which the system log records are not used is an initial start.

System activity keypoints

The recovery manager controls the recording of keypoint information, and the delivery of the information to the various resource managers at emergency restart.

The recovery manager provides the support that enables activity keypoint information to be recorded at frequent intervals on the system log. You specify the activity keypoint frequency on the AKPFREQ system initialization parameter. See the CICS System Definition Guide for details. Activity keypoint information is of two types:

1.A list of all the UOWs currently active in the system

2.Image-copy type information allowing the current contents of a particular resource to be rebuilt

During an initial phase of CICS restart, recovery manager uses this information, together with UOW-related log records, to restore the CICS system to its state at the time of the previous shutdown. This is done on a single backward scan of the system log.

Frequency of taking activity keypoints: You are strongly recommended to specify a nonzero activity keypoint frequency. Choose an activity keypoint frequency that is suitable for the size of your system log stream. Note that writing activity keypoints at short intervals improves restart times, but at the expense of extra processing during normal running.

The following additional actions are taken for files accessed in non-RLS mode that use backup while open (BWO):

vTie-up records are recorded on the forward recovery log stream. A tie-up record associates a CICS file name with a VSAM data set name.

vRecovery points are recorded in the integrated catalog facility (ICF) catalog. These define the starting time for forward recovery. Data recorded on the forward recovery log before that time does not need to be used.

Forward recovery logs

CICS writes VSAM forward recovery logs to a general log stream defined to the MVS system logger. You can merge forward recovery log data for more than one VSAM data set to the same log stream, or you can dedicate a forward recovery log stream to a single data set.

See “Defining forward recovery log streams” on page 116 for information about the use of forward recovery log streams.

User journals and automatic journaling

User journals and autojournals are written to a general log stream defined to the MVS system logger.

22CICS TS for z/OS 4.1: Recovery and Restart Guide