For more information on ON conditions, see the section ON in the chapter Statements and the section ONCODE Function in the chapter Open PL/I Built-Ins, both in your Open PL/I Language Reference Manual.
Note that the value returned by ONCODE for some conditions is implementation-dependent; in fact, some conditions that occur on one implementation may not be raised at all on another implementation, even by an identical source program run on both implementations. Further, subsequent releases of Open PL/I may change these ONCODE values. Therefore, to make programs more portable, avoid writing Open PL/I programs that depend on specific ONCODE return values to function properly; failing that, use replace constants to represent needed values so that implementation-specific values can be changed easily.