Two run-time system elements in a run unit can reference common data in the following circumstances:
- The data content of an external data record can be referenced from any run-time system element provided that element has described
that data record.
- If a program is contained in another program, both programs can refer to data possessing the global attribute either in the
containing program or in any program which directly or indirectly contains the containing program.
- The mechanism whereby a parameter value is passed by reference from an activating run-time system element to an activated
run-time system element establishes a common data item; the activated run-time system element, which can use a different identifier,
can refer to a data item in the activating run-time system element.