Hi LearningBee

Till 8i you needed to have a catalog or a separate database for RMAN to have many of the functionalities working.RMAN has undergone a major revamp in 9i.Most of the things now in 9i can be accomplished without using a catalog or a separate database.

You read the RMAN 9i Book by Mcgraw Hill Authored by robert freeman or the documentation.

regards
Hrishy