Internal trace table

Every CICS® region always has an internal trace table. The internal trace table resides in 64-bit z/OS® storage outside CICS DSAs. It is allocated at an early stage during CICS initialization, and it exists for the whole of the CICS run. The internal trace table is most useful for background tracing or when you do not need to capture an extensive set of trace entries. If you need to trace CICS system activity over a long period, or if you need many trace entries over a short period, one of the other trace destinations is likely to be more appropriate.

You can use the internal trace flag to control whether to record trace data in the CICS internal trace table. Even if internal trace has not been started for the CICS region, the internal trace table is used as a buffer for the other trace destinations. Trace entries are built there and copied to the auxiliary trace data sets or to GTF trace if those destinations are started.

Exception trace entries are always written to the internal trace table, even if no trace destinations are currently started. Other trace destinations that are currently started get the exception trace entry as well, but the entry always goes to the internal trace table even if you have turned tracing off completely. This function provides first failure data capture.

For a transaction dump, CICS copies the current internal trace table to produce the transaction dump trace table in 64-bit z/OS storage.

Size of the internal trace table

You use the TRTABSZ system initialization parameter to specify the size of the internal trace table at CICS startup. The default size is 12288 KB (12 MB). The range of value that you can set for the size of the internal trace table depends on the version of your CICS system. See TRTABSZ system initialization parameter for more information.

The internal trace table wraps when it is full. When the end of the table is reached, the next trace entry to be directed to the internal trace table goes to the start, and overlays the trace entry that was formerly there. You can increase or decrease the size of the internal trace table by using CETR while CICS is running, but if you do so, you lose all of the trace data that was present in the table at the time of the change.

Activating CICS internal trace

To activate CICS internal trace, you must at least switch on the main system trace flag (SYSTR=ON) and the internal trace flag (INTTR=ON). The trace data you get also depends on other system trace options that are in effect.

You can switch on or off CICS internal trace in the SIT for system initialization, or by using the CETR transaction for a running CICS system.

Formatting the internal trace table

You can format the internal trace table in two ways:
  • From a CICS system dump, by using the CICS print dump exit, DFHPDnnn, where nnn is a release identifier. For example, it is DFHPD760 for CICS TS beta.

    If the internal trace table is large, you can use trace selection parameters to reduce the number of trace entries that are formatted. See Selecting parts of the CICS internal trace table.

  • From a transaction dump, by using the CICS dump utility program, DFHDUnnn, where nnn is a release identifier. For example, it is DFHDU760 for CICS TS beta.