System tables are tables used to store information about the system (the system catalog) or an individual database (the database catalog). The system catalog consists of system tables found only in the master database. The database catalog consists of system tables found in every database.
In SQL Server 6.0, the addition of replication and the SQL Executive has added new system tables based on the type of database used in replication and scheduling of events.
The system tables have been categorized by the types of related information: