The advantage of using SVC 97 for breakpoints is that IDF can then debug code that uses z/OS subtasking or sets up (E)STAE or (E)SPIE exits. Also, IDF can debug ISPF dialogs.

The disadvantage is that you must install IDF in the z/OS Link List or your STEPLIB, or via the TSOLIB command. You cannot install it in a TASKLIB or ISPLLIB concatenation. The reason for this is that IDF must be invoked directly from TSO/E READY or from a CLIST that it is invoked from TSO/E READY. You cannot invoke IDF from a REXX EXEC or under ISPF except by using the TSOEXEC command. For an example of how to debug ISPF dialogs, see ISPF applications (TSO).