An input or output procedure that is referenced on a COBOL SORT or MERGE statement cannot directly or indirectly invoke another SORT or MERGE. When you use the VS COBOL II runtime library, a nested SORT or a MERGE statement like this was not diagnosed. However, Language Environment for z/OS detects the nested SORT or MERGE in a VS COBOL II program and issues message IGZ0173S before terminating the program.