Specifies the default catalog for the module. Catalogs are groups
    of schemas within a multischema database. If you omit the catalog
    name when specifying an object in a multischema database, SQL
    uses the default catalog name RDB$CATALOG. Databases created
    without the multischema attribute do not have catalogs. You
    can use the SET CATALOG statement to change the current default
    catalog name in dynamic or interactive SQL.