The format and content of run-time messages are different. If you have applications that analyze run-time messages, you must change the applications to allow for the differences. The differences include:
Details are provided in Language Environment Debugging Guide and Run-Time Messages.
Under Language Environment, run-time messages go to the MSGFILE destination specified in the run-time option MSGFILE. The default for MSGFILE destination is SYSOUT. The user output still goes to SYSPRINT. MSGFILE(SYSPRINT) is supported under Enterprise PL/I only after applying the PTFs for the runtime APAR PQ78307. For more information about the MSGFILE option, refer to z/OS Language Environment Programming Guide.