CICS Journal/User Log Help

In general, CICS regions refer to their system logs and general logs by an internal 8-character journal name.  For example, the internal name for the CICS system log is DFHLOG, and general logs are identified by journal names of the form DFHJnn, where nn is a number in the range 01 - 99.  CICS maps its internal 8-character journal names to MVS log streams by user-defined JOURNALMODEL resource definitions, in which you specify the journal name and the corresponding log stream name.

The JOURNALMODEL resource definition replaces entries in the journal control table, which is obsolete.

System logger is a set of services that allows an application to write, browse, and delete log data.  You can use system logger services to merge data from multiple instances of an application, including merging data from different systems across a sysplex.  It uses list structures to hold the logstream data from exploiters of the system logger.

Log streams are sequence of data blocks, with each log stream identified by its own logstream identifier--the log stream name (LSN).  Each log stream is written by the MVS system logger to a specified list structure in the coupling facility.

The CICS system log, forward recovery logs, autojournals, log of logs, and user journals map onto specific MVS log streams.

MVS log streams replace the CICS journal data sets.

The system logger component manages log streams based on the LOGR policy in the LOGR couple data set.  The LOGR policy includes:

• Log stream definitions
• Coupling facility list structure definitions
• Keywords

It's in the LOGR policy that keywords such as MAXBUFFSIZE, AVGBUFFSIZE, and LOGSNUM are defined.  To simplify the tool's interface, a design decision was made to externalize only those fields that could not default to a reasonable value.  As such, the following defaults are used for sizing a log structure when you click the Size Structure button:

• LOWOFFLOAD - specifies the point, in percent value of space consumed, where logger stops offloading coupling facility log data to the DASD log data sets for this log stream.  LOWOFFLOAD defaults to 0.

• HIGHOFFLOAD - specifies the point, in percent value of space consumed, where logger begins offloading coupling facility log data to the DASD log data sets for this log stream.  HIGHOFFLOAD defaults to 80.

Writes per second

The number of log blocks written to the log stream per second from a single system.

For more information about defining logstreams, refer to IBM publication z/OS MVS Setting up a Sysplex SA23-1399.

Maximum buffer size

Specifies the size, in bytes, of the largest log block that can be written to log streams. The maximum buffer size must be a value in the range 1 - 65532.

Average buffer size

Specifies the average size in bytes of log blocks written to all log streams.

Number of logstreams

Specifies the number of log streams allocated to a list structure. The number of logstreams must be a value in the range 1 - 512.