Auxiliary trace data sets

The auxiliary trace data sets are CICS-owned BSAM data sets named DFHAUXT and DFHBUXT. If you want to use auxiliary trace, you must create one or both of these data sets before you start CICS; you cannot create them while CICS is running.

The auxiliary trace data sets require two 4 KB data buffers in the CICS region's storage.

When you first start CICS auxiliary trace, any trace entries are directed to the initial auxiliary trace data set. If CICS terminated normally when auxiliary trace was last active, this is the auxiliary trace data set that was not being used at the time. Otherwise, it is the DFHAUXT data set. If you initialize CICS with auxiliary trace started, DFHAUXT is used as the initial auxiliary trace data set.

When you have two auxiliary trace data sets, you can choose from the following actions for CICS to take when one data set is full. You specify your chosen action using the auxiliary switch, which you can set using the AUXTRSW system initialization parameter or the CEMT transaction:

When the initial data set is full, no more trace entries are directed to the auxiliary trace data sets. (AUXTRSW=NO)
When the initial data set is full, then the other data set receives the next trace entries. When that one is full, no more trace entries are directed to the auxiliary trace data sets. (AUXTRSW=NEXT)
Auxiliary trace data is written alternately to each data set, and CICS switches from one to the other every time the current one becomes full. With this action selected, trace entries are eventually overwritten, as they are in the internal trace table. (AUXTRSW=ALL)

When auxiliary tracing is started or when it is paused, the auxiliary trace data set that is currently in use is open. When auxiliary tracing is stopped, the auxiliary trace data set is closed.

You can use auxiliary trace data sets to collect large amounts of trace data, provided that you initially define large enough data sets. For example, you might want to use auxiliary trace to track system activity over a long period of time, perhaps to solve an unpredictable storage violation problem. Auxiliary trace can be particularly useful if you are using CICS trace during startup, because of the high volume of trace entries that are written when CICS is initializing.

CICS provides a trace utility program, DFHTU700, that you can use to extract all or selected trace entries from auxiliary trace data sets, and format and print the data. You can select the trace entries based on the time when they were written, and the reports from the trace utility program include time stamps to help you match external events with a particular area of the trace.