The TGT and RSA conventions in Enterprise COBOL, COBOL for OS/390 & VM, and COBOL for MVS & VM are different than in VS COBOL II and COBOL/370. If you have COBOL applications that are coded to assume Register 9 or Register 13 values, you must change those programs so they do not have built-in assumptions about register values.
You can use the R15 slot in the previous save area to determine the entry point and signature information of the routine that owns the DSA.