When common areas (blank or named) are encountered in an overlay program, the common areas are collected as described previously (that is, the largest blank or identically named common area is used). The final location of the common area in the output module depends on whether INSERT statements were used to structure the program.
If INSERT statements are used to structure the overlay program, a named common area should either be part of the input stream in the segment to which it belongs or it should be placed there with an INSERT statement.
Because INSERT statements cannot be used for blank common areas, a blank common area should always be part of the input stream in the segment to which it belongs.
If INSERT statements are not used, and the control sections for each segment are placed or included between OVERLAY statements, the binder "promotes" the common area automatically. The common area is placed in the common segment of the paths that contain references to it so that the common area is in storage when needed. The position of the promoted area in relation to other control sections within the common segment is unpredictable.
If a common area is encountered in a module from the automatic call library, automatic promotion places the common area in the root segment. In the case of a named common area, this can be overridden by use of the INSERT statement.
