--- title: "Back Up and Restore of System Databases (SQL Server) | Microsoft Docs" ms.custom: "" ms.date: "03/07/2017" ms.prod: "sql-server-2014" ms.reviewer: "" ms.technology: backup-restore ms.topic: conceptual helpviewer_keywords: - "system databases [SQL Server], backing up and restoring" - "restoring system databases [SQL Server]" - "backing up [SQL Server], system databases" - "database backups [SQL Server], system databases" - "servers [SQL Server], backup" ms.assetid: aef0c4fa-ba67-413d-9359-1a67682fdaab author: MikeRayMSFT ms.author: mikeray manager: craigg --- # Back Up and Restore of System Databases (SQL Server) [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] maintains a set of system-level databases, s*ystem databases*, which are essential for the operation of a server instance. Several of the system databases must be backed up after every significant update. The system databases that you must always back up include **msdb**, **master**, and **model**. If any database uses replication on the server instance, there is a **distribution** system database that you must also back up. Backups of these system databases let you restore and recover the [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] system in the event of system failure, such as the loss of a hard disk. The following table summarizes all of the system databases. |System database|Description|Are backups required?|Recovery model|Comments| |---------------------|-----------------|---------------------------|--------------------|--------------| |[master](../databases/master-database.md)|The database that records all of the system level information for a [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] system.|Yes|Simple|Back up **master** as often as necessary to protect the data sufficiently for your business needs. We recommend a regular backup schedule, which you can supplement with an additional backup after a substantial update.| |[model](../databases/model-database.md)|The template for all databases that are created on the instance of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)].|Yes|User configurable1|Back up **model** only when necessary for your business needs; for example, immediately after customizing its database options.

**Best practice:** We recommend that you create only full database backups of **model**, as required. Because **model** is small and rarely changes, backing up the log is unnecessary.| |[msdb](../databases/msdb-database.md)|The database used by [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] Agent for scheduling alerts and jobs, and for recording operators. **msdb** also contains history tables such as the backup and restore history tables.|Yes|Simple (default)|Back up **msdb** whenever it is updated.| |[Resource](../databases/resource-database.md) (RDB)|A read-only database that contains copies of all system objects that ship with [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)]|No|-|The **Resource** database resides in the mssqlsystemresource.mdf file, which contains only code. Therefore, [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] cannot back up the **Resource** database.

Note: You can perform a file-based or a disk-based backup on the mssqlsystemresource.mdf file by treating the file as if it were a binary (.exe) file, instead of a database file. But you cannot use [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] restore on the backups. Restoring a backup copy of mssqlsystemresource.mdf can only be done manually, and you must be careful not to overwrite the current **Resource** database with an out-of-date or potentially insecure version.| |[tempdb](../databases/tempdb-database.md)|A workspace for holding temporary or intermediate result sets. This database is re-created every time an instance of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] is started. When the server instance is shut down, any data in **tempdb** is deleted permanently.|No|Simple|You cannot back up the **tempdb** system database.| |[Configure Distribution](../replication/configure-distribution.md)|A database that exists only if the server is configured as a replication Distributor. This database stores metadata and history data for all types of replication, and transactions for transactional replication.|Yes|Simple|For information about when to back up the **distribution** database, see [Back Up and Restore Replicated Databases](../replication/administration/back-up-and-restore-replicated-databases.md).| 1 To learn the current recovery model of the model, see [View or Change the Recovery Model of a Database (SQL Server)](view-or-change-the-recovery-model-of-a-database-sql-server.md) or [sys.databases (Transact-SQL)](/sql/relational-databases/system-catalog-views/sys-databases-transact-sql). ## Limitations on Restoring System Databases - System databases can be restored only from backups that are created on the version of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] that the server instance is currently running. For example, to restore a system database on a server instance that is running on [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] SP1. - To restore any database, the instance of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] must be running. Startup of an instance of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] requires that the **master** database is accessible and at least partly usable. If **master** becomes unusable, you can return the database to a usable state in either of the following ways: - Restore **master** from a current database backup. If you can start the server instance, you should be able to restore **master** from a full database backup. - Rebuild **master** completely. If severe damage to **master** prevents you from starting [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)], you must rebuild **master**. For more information, see [Rebuild System Databases](../databases/system-databases.md). > [!IMPORTANT] > Rebuilding **master** rebuilds all of the system databases. - Under some circumstances, problems recovering the model database may require rebuilding the system databases or replacing the mdf and ldf files for the model database. For more information, see [Rebuild System Databases](../databases/system-databases.md). ## Related Tasks - [Create a Full Database Backup (SQL Server)](create-a-full-database-backup-sql-server.md) - [Complete Database Restores (Simple Recovery Model)](complete-database-restores-simple-recovery-model.md) - [Restore the master Database (Transact-SQL)](restore-the-master-database-transact-sql.md) - [View or Change the Recovery Model of a Database (SQL Server)](view-or-change-the-recovery-model-of-a-database-sql-server.md) - [Move System Databases](../databases/move-system-databases.md) ## See Also [Distribution Database](../../relational-databases/replication/distribution-database.md) [master Database](../databases/master-database.md) [msdb Database](../databases/msdb-database.md) [model Database](../databases/model-database.md) [Resource Database](../databases/resource-database.md) [tempdb Database](../databases/tempdb-database.md)