Logstream statistics

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

Log stream statistics contain data about the use of each log stream including the following:
  • The number of write requests to the log stream
  • The number of bytes written to the log stream
  • The number of log stream buffer waits
  • The number of log stream browse and delete requests.

The CICS system log stream statistics for the last three items on this list are always zero.

Journalnames are a convenient means of identifying a destination log stream that is to be written to. CICS applications write data to journals using their journalname. CICS itself usually uses the underlying log stream name when issuing requests to the CICS log manager, and this must be considered when interpreting journalname and log stream resource statistics. For example, the statistics might show many operations against a log stream, but relatively few, if any, writes to a journalname which maps to that log stream. This indicates that it is CICS that accesses the resource at the log stream level, not an application writing to it through the CICS application programming interface. The results can typically be seen when examining the journalname resource statistics for DFHLOG and DFHSHUNT, and comparing them with the resource statistics for their associated CICS system log streams.

For more information about logging and journaling, see Logging and journaling performance.