Database System Catalogs

Each Oracle database runs on one centralized system catalog, or data dictionary, which resides in the SYSTEM tablespace. Each Microsoft SQL Server 7.0 database maintains its own system catalog, which contains information about:

• Database objects (tables, indexes, stored procedures, views, triggers,
  and so on).
• Constraints.
• Users and permissions.
• User-defined data types.
• Replication definitions.
• Files used by the database.

SQL Server also contains a centralized system catalog in the master database, which contains system catalogs as well as some information about the individual databases:

• Database names and the primary file location for each database.
• SQL Server login accounts.
• System messages.
• Database configuration values.
• Remote and/or linked servers.
• Current activity information.
• System stored procedures.

Like the SYSTEM tablespace in Oracle, the SQL Server master database must be available to access any other database. As such, it is important to protect against failures by backing up the master database after any significant changes are made in the database. Database administrators can also mirror the files that make up the master database.