Under Language Environment, there is a small difference in the timing of when some run-time messages are issued for conditions with ON-units:
This change gives you the chance to handle a condition (and issue your own message if you wish) and to continue your application via a GOTO without the run-time also issuing its own message.
There is no change to the run-time behavior when there is no ON-unit.
Also, the SNAP traceback message produced by ON ERROR SNAP continues to be issued before the ERROR ON-unit receives control.
When running Enterprise PL/I programs under Language Environment, some file I/O errors are now detected during the OPEN process, which results in a different but more meaningful error message and error code. As a result, the error will result in an UNDEFINEDFILE condition instead of a TRANSMIT or other condition that was received with older PL/I.