You create a catalog by defining its structure with the access method services DEFINE USERCATALOG command. The ICFCATALOG parameter is the default. DEFINE USERCATALOG VOLCATALOG defines a tape volume catalog that only contains tape library and tape volume entries. Access method services can also be used to define catalog aliases (with DEFINE ALIAS), and VVDSs (with DEFINE CLUSTER). Alias is not supported for tape volume catalogs.

Before you define a catalog, determine how large you want the catalog to be, and on which volume you want to place it. Also, determine the appropriate performance attributes for the catalog. All of these subjects are covered in this chapter.

See Setting the Catalog Control Interval and Area Size for information on choosing an appropriate control interval size for the index.