When DADSM scratch is called, IGGDASU3 receives control immediately after scratch processing completes.
When DADSM rename is called, IGGDARU3 receives control immediately after rename processing completes.
The DASSVCEP flag bit in the DASFLAG6 of the scratch parameter list, and the DARSVCEP flag bit in the DARFLAG4 field of the rename parameter list indicate whether the function was called through an SVC. You might test these bits in your exit routines to determine how the DADSM function was called.