What are the SQL Server system databases and can you outline the general functionality of each database?

What are the SQL Server system databases and can you outline the general functionality of each database?
  • Master - Database responsible for SQL Server instance related data.  You can also think of this database corresponding to the Windows SQL Server service account.
  • Resource - Database responsible for SQL Server system objects.  This database was introduced in SQL Server 2005 and is intended to ease the upgrade and rollback of SQL Server system objects.
  • Model - Template database for the creation of new user defined databases.
  • MSDB - Database responsible for SQL Server Agent related data such as Jobs, Alerts, Operators, etc.
  • TempDB - Temporary database to store temporary tables (#temptable or ##temptale), table variables, cursors, work tables, row versioning, create or rebuild indexes sorted in TempDB, etc.  Each time the SQL Server instance is restarted all objects in this database are destroyed, so permanent objects cannot be created in this database.
  • Distribution - Database responsible for managing replicated data.  This database could reside on the publisher or subscriber.

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