Using the DL/I trace facility

The DL/I trace facility is an important diagnostic tool that can help you determine the cause of a problem. Frequently, a problem occurs as a result of the interaction between two separate tasks. Interpreting the DL/I trace entries can be the best way of determining what each task was doing, and when.

Example for using the DL/I trace facility

An IMS Fast Path application receives an abend 1027, and the user reports the problem to the support staff. Some of the steps the diagnostician might take are:

  1. Find the abend code in IMS Version 15 Messages and Codes, Volume 3: IMS Abend Codes. This information indicates that the return code is in register 15.
  2. Register 15 in the dump contains a value of X'0D.'

    IMS Version 15 Messages and Codes, Volume 3: IMS Abend Codes indicates that this return code indicates that an enqueue or dequeue call was issued by module DBFBENQ0, and the return code from DFSLRH00 was X'12,' which indicates an invalid call.

  3. Look at the DL/I trace to determine what resource was involved (if the DL/I trace was on at the time of the abend). If the DL/I trace was not on, it might be necessary to create the problem again with the DL/I trace facility on.

    The list of trace entry IDs in DL/I trace formats indicates that one of the trace entries is Exclusive control ENQ/DEQ PI trace entry (The X'CA' trace entry for Fast Path calls). This is a good place to start the DL/I trace analysis.

What you learn from the DL/I trace might help you to:

  • Identify and resolve an application error.
  • Review APAR descriptions to see if this problem has occurred previously.
  • Report the problem to IBM Software Support.