The OMVS SECTRACE default destination is the system log. The output is more readable if it is put to a dataset.
An OMVS SECTRACE can be set as follows:
The dataset specified in the dsn parm must be pre-allocated. There is a job to allocate this dataset in the INITSECD member of SAMPJCL. Run that job before you set the SECTRACE if you want the trace records to go to a dataset. Otherwise, they will go to the system log.
The documentation on the OMVS SECTRACE is in the ACF2 System Programmer Guide Chapter 6, under "Tracing UNIX System Services (OMVS)".