OVERLAY statement

We do not recommend using the INSERT and OVERLAY statements for program objects. The binder supports the overlay format for compatibility only. For more information on the use of the OVERLAY statement, see Designing and specifying overlay programs.

The OVERLAY statement indicates the beginning of an overlay segment and, optionally, also of an overlay region. Because a segment or a region is not named, you identify it by giving its origin (or load point) a symbolic name. This name is then used on an OVERLAY statement to signify the start of a new segment beginning at that origin. The syntax of the OVERLAY statement is:

OVERLAY          symbol[(REGION)]

symbol: The symbolic name assigned to the origin of a segment. This symbol is not related to external symbols in the module.
(REGION): Specifies the origin of a new region, as well as a segment.

Placement: The OVERLAY statement must precede the first module of the next segment, the INCLUDE statement specifying the first module of the segment, or the INSERT statement specifying the control sections to be positioned in the segment.

Note:

The OVLY option must be specified on the EXEC statement when OVERLAY statements are to be used.
The sequence of OVERLAY statements should reflect the order of the segments in the overlay structure from top to bottom, left to right, and region by region.
No OVERLAY statement should precede the root segment.