SAS/IML storage catalogs are specially structured SAS files that are located in a SAS data library. A SAS/IML catalog contains entries that are either matrices or modules. Like other SAS files, SAS/IML catalogs have two-level names in the form libref.catalog. The first-level name, libref, is a name assigned to the SAS data library to which the catalog belongs. The second-level name, catalog, is the name of the catalog file.

The default libref is initially SASUSER, and the default catalog is IMLSTOR. Thus, the default storage catalog is called SASUSER.IMLSTOR. You can change the storage catalog with the RESET STORAGE command (see the discussion of the RESET statement in Chapter 24).

By using this command, you can change either the catalog or the libref.

When you store a matrix, IML automatically stores the matrix name, its type, its dimension, and its current values. Modules are stored in the form of their compiled code. Once modules are loaded, they do not need to be parsed again, making their use very efficient.