Trace activation

You can activate trace using the Fast Path Transaction Retry, the CCTL DRA thread, or using the /TRA SET ON TABLE FAST command.

  • The Fast Path Transaction Retry function normally attempts to activate Fast Path external trace when a transaction is retried in an MPP or IFP region after an abend in Fast Path code. In this case, the trace is activated internally for the dependent region that is executing the retry and not for other dependent regions. The trace is deactivated after one retry attempt. The Fast Path Transaction Retry function dynamically allocates an FPTRACE DD statement as a JES SPOOL file and closes and deallocates an FPTRACE DD statement when the trace is deactivated at the end of the retry operation. The intent of the Fast Path Transaction Retry function is to provide first-failure data capture.
  • A CCTL DRA thread can also request that Fast Path external trace be activated for a particular thread during the create thread process.
  • The trace can also be activated with a /TRA SET ON TABLE FAST command. The Fast Path external trace writes diagnostic data to a FPTRACE DD statement in the dependent region JCL. After the trace is activated, the presence or absence of the FPTRACE DD statement determines whether data is traced for each active dependent region, including CCTL DRA threads. A spool file (SYSOUT=x) can be used for a FPTRACE DD statement, or a DASD file can be used. DCB attributes are forced to LRECL=133,BLKSIZE=133,RECFM=FA by IMS when the DCB is opened.
Recommendations:
  • Use a spool file (SYSOUT=x) rather than a disk file. A certain amount of data related to the trace activation itself is traced (written to FPTRACE) before the determination is made that the trace is active or inactive.
  • Do not include an FPTRACE DD statement in your standard dependent region JCL. Add it only as required and then remove it after the trace data is collected.