Interpreting API Trace Data

The API trace facility writes trace data in the form of ATB6xxxxI messages; illustrates the format and explains the contents of each message. These messages are stored in a particular API trace data set, in a format that you can view with an editor or browser, once all tracing activity for the data set has stopped.

For a particular LU and TP (and possibly USERID) combination, these ATB6xxxxI messages (or trace entries) document:

ATBTRACE START and STOP requests, including all parameters and their values specified for each request.
The contents of FMH-5 records exchanged between conversing TPs, excluding passwords.
Both entry to and return from a supported APPC/MVS or CPI-C service.
The number of trace entries lost if APPC/MVS had to temporarily suspend tracing activity.

Depending on the location of the TP's partners, you might have to compare the contents of more than one trace data set; perhaps comparing the API trace data with trace data from a facility provided on a platform other than MVS. The format of API trace data is similar to that provided by CM/2 on OS/2, so you can more easily diagnose problems between APPC/MVS TPs and their partners on OS/2.