How CMS Handles Objects in Logical Saved Segments
When a logical saved segment is loaded, the MODULE or TEXT files contained within it are established as nucleus extensions or subcommand processors, execs are established as EXECs-in-storage, callable services libraries are available for the GLOBAL CSLLIB and RTNLOAD commands, application language information is activated, and user object load routines are called.
All application language information whose languages match the current system language is added to the active set of applications. Thus, the application does not need to issue a SET LANGUAGE command with the ADD option. When a SET LANGUAGE command is issued that changes the current system language, all application language information for the old language is dropped, and any language information that matches the new system language and is in a currently loaded logical saved segment is automatically added.
Logical saved segments and the objects in them are loaded last-in-first-out (LIFO). Nucleus extensions, subcommand processors, and execs (all of which are in a saved segment that has been loaded) override previous definitions with the same name. To reactivate previous definitions, you can drop saved segment-resident nucleus extensions (using NUCXDROP) or execs (using EXECDROP), or purge the saved segment. After an object in a saved segment has been dropped, the saved segment must be purged and reloaded to reactivate the object.
Objects in other logical saved segments within the physical saved segment are not processed.