System catalog tables

Each database includes a set of system catalog tables, which describe the logical and physical structure of the data. The database manager creates and maintains an extensive set of system catalog tables for each database. These tables contain information about the definitions of the database objects, such as user tables, views, and indexes, as well as security information about the authority that users have for these objects. They are created when the database is created, and are updated in the course of normal operation. You cannot explicitly create or drop them, but you can query and view their contents using the catalog views.