PL/I condition handling semantics

Enterprise PL/I for z/OS condition handling semantics are the same as PL/I except that Enterprise PL/I for z/OS, like C, ignores any hardware fixed-point overflow exceptions.

When an exception occurs in a PL/I routine, PL/I language semantics for handling the condition prevail. Therefore, the behavior of PL/I condition handling in applications consisting of only PL/I routines is unchanged under Language Environment.

In PL/I, you handle all runtime conditions by writing ON-units. An ON-unit is a procedure that is established in a block when the ON statement for the ON-unit is run. The ON-unit itself runs when the specified condition in the ON statement is raised. The establishment of an ON-unit applies to all dynamically descendent (inherited from calling procedure) blocks of the block that established it; a condition occurring in a called procedure could result in an ON-unit being run in the caller.

This section provides a high-level view of how condition handling works if an exception occurs in a PL/I routine, and only PL/I routines are on the stack. For a more detailed explanation of PL/I condition handling, refer to PL/I for MVS & VM Language Reference. For details about how PL/I condition handling works in an ILC application, see z/OS V2R1.0 Language Environment Writing Interlanguage Communication Applications.