Other programs besides CICS can use the z/OS GTF trace destination. This lets you integrate CICS trace entries with those from other programs. A single GTF trace data set could, for example, contain trace entries made by CICS and VTAM. Another reason to use the GTF trace destination is that performance overhead may be lower than using CICS auxiliary trace destination.
If the performance overhead caused by CICS tracing is an issue, you may wish to consider limiting the amount of CICS tracing to just one transaction. You can set up this special tracing using the CETR transaction. Once in the first CETR panel, turn off the master system trace flag so the rest of the transactions aren’t traced. Then, turn on special tracing for the transaction you want to trace. Hit PF4 to list the components, set up the special tracing to reflect the tracing you want to do on the transaction, and then press enter to make the changes. Once the special tracing is set up as desired, return to the main CETR screen by hitting PF3. Next, hit PF5 to go to the transaction and terminal options. Enter the transaction ID and set the transaction status to “special.” Then return to the main CETR screen by hitting PF3. On the main CETR screen, set internal trace status and auxiliary or GTF trace status to get started. The special tracing for the selected transaction should be written to the auxiliary or GTF trace and the standard tracing for the rest of the transactions will be suppressed because the master system trace flag is off. This process is described in the CICS Transaction Server 3.1 Problem Determination Guide.
Before you can look at your trace output, you need to format it. Formatting depends on which trace destination you selected. The following examples are for CICS Transaction Server 3.1 and have suffices of 640 (its CICS release number).
The internal trace table can be formatted from a:
- CICS system dump using the CICS dump verbexit, DFHPD640
- Transaction dump using the CICS dump utility program, DFHDU640.
Auxiliary trace can be formatted using the CICS trace utility program, DFHTU640. CICS GTF trace can be formatted using the CICS-supplied routine, DFHTG640. For more details, see the CICS Transaction Server 3.1 Operations and Utilities Guide.
You can specify abbreviated, short, or extended trace formatting to give you varying levels of information and detail in your output. Typically:
- Abbreviated format trace gives you one line of trace per entry
- Short format provides two lines of trace per entry
- Extended format provides many lines of trace per entry.
When reading a CICS trace, it’s often useful to start with the abbreviated trace formatting to give you an overview and identify which trace entries are of interest. Each trace entry has its sequence number at the end of each entry. This number is always enclosed by equal signs in the form of, for example, ‘=000005=.’ If you wished to find equivalent trace entry ‘=000005=’ in the extended trace, then a search on ‘=000005=’ would find the fully interpreted version of that same trace entry. Sequence numbers are unique in a given trace and let you specifically identify each trace entry formatted from the trace destination.
Figure 2 shows an edited example of some abbreviated CICS trace entries. The trace formatter gives the task number (00028 in this example), TCB being executed on, and the domain and identifier of the trace entry, as well as a readable interpretation of the trace entry itself. For example, the trace entry with number =000530= was issued by task 00028, running under the QR TCB, and represents an EXEC CICS command (it has the trace point of AP 00E1).