A GDS state, deferred roll-in, preserves JCL that creates and references GDSs. When a new GDS is created, it is cataloged but assigned a status of deferred roll-in, so that the oldest generation is not deleted. The new GDS is only rolled in at disposition processing at job or step termination in an existing job when you code DISP=(OLD,CATLG) in a different job or use the access method services ALTER ROLLIN command. This has special implications on restarts after a job failure.