below are two sentences found on the web:
When the Enterprise COBOL, COBOL for OS/390 & VM, or COBOL for MVS & VM program is running, R13 has the address of a DSA (dynamic save area) for the COBOL program. The address of the COBOL program's TGT is located at x"5C" in the DSA.
If R13 has the address of a save area associated with a called assembler program or COBOL runtime routine, use the save area back chain to find the DSA for the COBOL program. Then add x"5C" to find the address of the TGT.
can i samply think DSA = RSA(register save area)?
besides, can somebody explain what's the main purpose of TGT and DSA?