Compatibility of program object formats

Downward Compatibility: The default program object format is the earliest which will support the function requested by the contents of the input modules and the processing directives.
Upward Compatibility: All earlier PM functions, interfaces, formats and user job streams should work compatibly with the current release. There will be some changes in report formats and messages, where changes are necessary for this new function.
Only PM1 format program objects support overlay format. The binder will automatically produce a PM1 version of the program object if overlay is requested and the SYSLMOD data set is a PDSE.
During API processing for “intent access” the module will be saved in the same format it had on input if followed by a copy operation. During API processing for “intent bind” (and both libraries are PDSEs), the module will be saved in the lowest format program object which will support the requested functions unless overridden with the COMPAT option.
If the user specifies a COMPAT value and attempts to use functions not supported by that level, the save will fail with RC=12.