The database catalog of a database instance consists ofmetadata in which definitions of database objects such as basetables, views (virtual tables), synonyms, value ranges, indexes,users, and user groups are stored.
The SQL standard specifies a uniform means to access thecatalog, called the INFORMATION_SCHEMA, but not all databasesfollow this, even if they implement other aspects of the SQLstandard. For an example of database-specific metadata accessmethods, see Oracle metadata.