Master :-
The Master database is the logical repository for the system objects residing in the sys schema. In SQL Server 2000 and previous editions of SQL Server, the Master database physically stored all of the system objects.
Prominent Functionality:
1) Per instance configurations
2) Databases residing on the instance
3) Files for each database
4) Logins
5) Linked\Remote servers
6) Endpoints
Model:
Template database for all user defined databases.
Additional Points:
The database configurations such as the recovery model for the Model database are applied to future user defined databases
MSDB:
Primary database to manage the SQL Server Agent configurations
Stores:
1) SQL Server Agent Jobs, Operators and Alerts
2) DTS Package storage in SQL Server 7.0 and 2000
3) SSIS Package storage in SQL Server 2005
4) Stores backup and restore information
TempDB:
Temporary database to store temporary tables (#temptable or ##temptable), 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.
1) Tempdb stores temporary objects
2) Tempdb is used for sortings and mergings
3) From SQL Server 2005 onwards, SQL Server uses Tempdb as Version Store i.e. for Row Versioning
4) Index rebuild and Sorts are performed in Tempdb
Resource:
The Resource database is responsible for physically storing all of the SQL Server 2005 system objects. This database has been created to improve the upgrade and rollback of SQL Server system objects with the ability to overwrite only this database.
Additional Points:
1) Introduced in SQL Server 2005 to help manage the upgrade/rollback of system objects
2) Prior to SQL Server 2005 the system related data was stored in the master database
3) Read-only database and also Hidden db that is not accessible via the SQL Server 2005 tool set
4) The database ID for the Resource database is 32767
5) The Resource database does not have an entry in master.sys.databases
