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YOU ARE HERE: HOME Questions What are System Databases What are the significance of those databases Master Model Resource Tempdb

System Databases in SQL Server and It's Significance

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What are System Databases? What are the significance of those databases (Master, Model, Resource, Tempdb and MSDB)?

Answer 1)

master database

The Master database is the heart and soul of SQL Server. It basically records all the system level information. Every instance of SQL Server will have an independent Master database; as it captures instance level configuration information. The information which is captured in the Master database includes SQL Server instance level configurations, linked server configurations, SQL Server Logins, Service Broker Endpoints, System Level Stored Procedures, and System level Functions etc. The system and user databases related information such as name and location for user and system database are captured in Master database.

If master database is corrupted or if it is not available then the SQL Server Service will not start. In SQL Server 2005 and later versions the system objects are stored in Resource Database rather than in Master Database. The Master database is created using Simple Recovery Model.

msdb database

SQL Server Agent uses MSDB database to store information related to the configuration of SQL Server Agent Jobs, Job schedules, Alerts, Operators etc. MSDB also stores information related to configuration of Service Broker, Log Shipping, database backups and restore information, Maintenance Plan Configuration, Configuration of Database Mail, Policy Bases Information of SQL Server 2008 etc. 

If the MSDB database is corrupted or damaged then scheduling information used by SQL Server Agent will be lost. This will result in the failure of all scheduled activities.

model database

The Model database is basically used as a template when creating databases in SQL Server. Basically SQL Server takes a copy of Model database whenever a user tries to create a new database in SQL Server. This also means that if a user creates any tables, stored procedures, user defined data types or user defined functions within a Model database; then those objects will be available in every newly created database on that particular instance of SQL Server.

If the Model database is damaged or corrupted then SQL Server Service will not start up as it will not be able to create the tempdb database.

Resource database

The Resource database is a read only, hidden system database that contains all the SQL Server system objects such as sys.objects which are physically available only in the Resource database, even though they logically appear in the SYS schema of every database. The Resource Database does not contain any user data or any user metadata. By design, the Resource database is not visible under SQL Server Management Studio’s Object Explorer | Databases | System Databases Node.

The DBA shouldn’t rename or move the Resource Database file. If the files are renamed or moved from their respective locations then SQL Server will not start. The other important thing to be considered is not to put the Resource Database files in a compressed or encrypted NTFS file system folders as it will hinder the performance and will also possibly  prevent upgrades.

tempdb database

In SQL Server, TempDB database is recreated every time SQL Server Service is restarted. This also means that the some of the settings of Model database are also used when TempDB is created. Is a workspace for holding temporary objects or intermediate result sets.

  Asked in:  TCS (Tata Consultancy Services)   Expertise Level:  Expert
  Last updated on Monday, 13 June 2011
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