Where dumps are written

Transaction dumps and system dumps are written to different destinations.

• Transaction dumps go to a pair of CICS BSAM data sets, with DD names DFHDMPA and DFHDMPB. Some of the attributes of these data sets can be set by system initialization parameters, some can be set dynamically using CEMT SET DUMPDS or EXEC CICS SET DUMPDS, and all can be inquired on by using CEMT INQ DUMPDS or EXEC CICS INQUIRE DUMPDS. DFHDMPA and DFHDMPB have the following attributes:
  • CURRENTDDS status. This tells you the data set that is currently active, which is the one where transaction dumps are currently written.

    You can use the system initialization parameter DUMPDS to specify the transaction dump data set that is to be opened during initialization. You can use the CEMT SET DUMPDS transaction or an EXEC CICS SET command to switch the dump data sets.

  • One of the statuses OPEN or CLOSED. A transaction dump data set must be OPEN if it is to be written to.
  • The current data set has one of the statuses AUTOSWITCH or NOAUTOSWITCH. You can set the status during system initialization using the DUMPSW system initialization parameter, and you can set it dynamically using the CEMT transaction or an EXEC CICS SET command.

    If the status is AUTOSWITCH, a switch is made automatically to the other dump data set when the current one becomes full, and subsequent transaction dumps are written to the new dump data set. The overflowing transaction dump is written in its entirety to the new dump data set.

    The dump data set being switched to does not inherit the AUTOSWITCH status, to prevent data in the first dump data set from being overwritten by another switch. You need to reset the AUTOSWITCH status explicitly, if you want it.

    If the status is NOAUTOSWITCH, a switch is not made when the current dump data set becomes full, so no more transaction dumps can be written.

• CICS system dumps are written to MVS dump data sets. CICS can write only one system dump to any individual dump data set.

  If another address space is already taking an SDUMP when CICS issues the SDUMP macro, the request fails but is automatically retried. You can use the DURETRY system initialization parameter to define the total time that CICS is to continue trying to take an SDUMP.

  If CICS tries to take an SDUMP when all the dump data sets are full, the dump is lost. Because of this, it is advisable to monitor the number of full data sets, and to take copies of dumps before processing them, so that you can free the dump data sets for reuse.