A catalog is a data set that contains information about other data sets. It provides users with the ability to locate a data set by name, without knowing where the data set resides. By cataloging data sets, your users will need to know less about your storage setup. Thus, data can be moved from one device to another, without requiring a change in JCL DD statements that refer to an existing data set.

Cataloging data sets also simplifies backup and recovery procedures. Catalogs are the central information point for data sets; all VSAM data sets must be cataloged. In addition, all SMS-managed data sets must be cataloged.

DFSMS allows you to use catalogs for any type of data set or object. Many advanced functions require the use of catalogs, for example, the Storage Management Subsystem.