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Database Mirroring

Database mirroring is a primarily software solution for increasing database availability. Mirroring is implemented on a per-database basis and works only with databases that use the full recovery model. The simple and bulk-logged recovery models do not support database mirroring. Database mirroring is supported in SQL Server Standard and Enterprise.

Database mirroring offers substantial availability and provides an easy-to-manage alternative or supplement to failover clustering or log shipping. When a database mirroring session is synchronized, database mirroring provides a hot standby server that supports rapid failover with no loss of data from committed transactions. During a typical mirroring session, after a production server fails, client applications can recover quickly by reconnecting to the standby server.


You cannot mirror the master, msdb, temp, or model databases.

In This Section

  • Database Mirroring Overview
    Introduces the components of database mirroring.

  • Database Mirroring Sessions
    Describes how database mirroring sessions operate: concurrent sessions, the threads created for each session, and the prerequisites for a session, and so on.

  • Database Mirroring Operating Modes
    Contains information about the synchronous and asynchronous operating modes for database mirroring sessions, and about switching partner roles during a database mirroring session.

  • Role Switching During a Database Mirroring Session
    Contains information about switching partner roles during a database mirroring session, including automatic failover, manual failover, and forced service (with possible data loss). Also, contains information about estimating the interruption of service during role switching.

  • Automatic Page Repair During a Database Mirroring Session
    Describes how a database mirroring partner running on SQL Server 2008 or later versions responds to errors that prevent reading a data page.

  • Mirroring States
    Describes the possible mirroring states of a mirrored database.

  • Database Mirroring Deployment
    Contains information about setting up database mirroring and connecting clients to a mirrored database.

  • Database Mirroring Administration
    Contains information about how pausing, resuming, and stopping a database mirroring session, and monitoring your database mirroring sessions.

  • Monitoring Database Mirroring
    Contains information about using Database Mirroring Monitor or the dbmmonitor stored procedures to monitor database mirroring or sessions.