Writing trace tables externally
You can write the in-memory trace tables to an external device, tape data set, or to the OLDS (online log data set).
When the IMS MTO starts IMS trace table traces with the LOG option, the following selection order determines where the
external traces are written.
- DASD JCL
- DD statements are checked to verify that DFSTRA01 or DFSTRA02 are present. If either or both are present, the JCL specified DASD external trace data sets are used if possible.
- DASD MDA
- An attempt is made to dynamically allocate and open DFSTRA01 and DFSTRA02 by using dynamic allocation members. If either or both dynamic allocations succeed, the DASD external trace data sets are used if possible.
- TAPE MDA
- An attempt is made to dynamically allocate and open member DFSTRA0T. If the dynamic allocation succeeds, the external trace tapes are used if possible.
- IMS log data set
- The IMS log data set is used for external trace. Because of the performance effects of logging trace data to the online log data set, the operator is asked to approve tracing to the online log data set when external trace data sets cannot be used.
To print the X'67FA' records, use the File Select and Formatting Print utility (DFSERA10), and specify exit DFSERA60 to format the trace entries.
DFSTRA01 and DFSTRA02 are the external trace data sets used by the IMS online systems. The trace data sets are used when the trace table OUT parameter is used in the DFSVSMxx options statement, or when the /TRACE SET ON TABLE nnn OPTION LOG command is used. The trace data sets are used in a wrap-around fashion. For example, when DFSTRA01 fills, DFSTRA02 is used; when DFSTRA02 fills, DFSTRA01 is used.
Recommendation: You must remember to offload the trace data set before
it is reused. Use the IEBGENER utility to offload the data set.