Invoking the target program
Properly invoking IDF can easily get you breakpoints in modules that get loaded by another. For example, here is what you do if you want to debug the program XYZZY that runs as an ISPF dialog, using TSO TEST:
TEST 'SYS1.ISP.LINKLIB(ISPF)' CP
ISPSTART PGM(XYZZY)
AT XYZZY.XYZZY.+0 DEFER
Here is what you do using using ASMIDF:
ASMIDF ISPF (COMMAND/ISPSTART PGM(XYZZY)
once in IDF,
DBREAK (XYZZY.)
This can only be done if you are using SVC 97 for breakpoints.