Monitoring the logger environment

CICS® collects statistics on the data written to each journal and log stream; this data can be used to analyze the activity of a single region. However, because general log streams can be shared across multiple MVS™ images, it can be more useful to examine the statistics generated by MVS.

The MVS system logger writes SMF Type 88 records containing statistics for each connected log stream. MVS supplies in SYS1.SAMPLIB a sample reporting program, IXGRPT1, that you can use as supplied, or modify to meet your requirements. Alternatively, you could use some other SMF reporting program. For information about the SMF Type 88 records and the sample reporting program, see the z/OS MVS System Management Facilities (SMF) manual.

The main items that should be monitored routinely are:

If these events occur frequently, this indicates that the logger cannot write data to secondary storage quickly enough to keep up with incoming data, which causes CICS to wait before it can write more data. Consider the following solutions to resolve such problems:

For CICS system logs, the best performance is achieved when CICS can delete log tail data that is no longer needed before it is written to secondary storage by the MVS system logger. To monitor that this is being achieved, your reporting program should examine the numbers in the SMF88SIB and SMF88SAB SMF Type 88 records. These values indicate:

SMF88SIB
Data deleted from primary storage without first being written to DASD offload data sets. For a system log stream, this value should be high in relation to the value of SMF88SAB. For a general log stream, this value should normally be zero.
SMF88SAB
Data deleted from primary storage after being written to DASD offload data sets. For a system log stream, this value should be low in relation to the value of SMF88SIB. For a general log stream, this value should normally be high.
Note:
In any SMF interval, the total number of bytes deleted from primary storage (SMF88SIB plus SMF88SAB) may not match the total number of bytes written to secondary storage, because data is only written to offload data sets and then deleted from primary storage when the HIGHOFFLOAD threshold limit is reached.

If the SMF88SAB record frequently contains high values for a CICS system log:

Related tasks
Logging and journaling: performance considerations
Performance implications of average blocksize
Performance implications of the number of log streams in the coupling facility structure
Setting LOWOFFLOAD and HIGHOFFLOAD parameters on log stream definition
Tuning the size of staging data sets
Setting the activity keypoint frequency (AKPFREQ)
Specifying the log defer interval (LGDFINT)
Tuning for DASD-only logging
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