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.

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.