manually-fail-over-a-database-mirroring-session-transact-sql.md

title	Manually fail over a database mirror to partner
description	Instructions to manually fail over a principle database mirror to a secondary partner using Transact-SQL (T-SQL).
ms.custom	seo-lt-2019
ms.date	03/14/2017
ms.prod	sql
ms.prod_service	high-availability
ms.reviewer
ms.technology	database-mirroring
ms.topic	conceptual
helpviewer_keywords	failover [SQL Server], database mirroring manual failover [SQL Server] database mirroring [SQL Server], failover
ms.assetid	36218d61-b5f5-4194-905a-608e0e903db4
author	MikeRayMSFT
ms.author	mikeray

Manually Fail Over a Database Mirroring Session (Transact-SQL)

[!INCLUDE SQL Server] When the mirrored database is synchronized (that is, when the database is in the SYNCHRONIZED state), the database owner can initiate manual failover to the mirror server. Manual failover can be initiated only from the principal server.

To manually fail over a database mirroring session

1. Connect to the principal server.

2. Set the database context to the master database:

   USE master;

3. Issue the following statement on the principal server:

   ALTER DATABASE database_name SET PARTNER FAILOVER, where database_name is the mirrored database.

   This initiates an immediate transition of the mirror server to the principal role.

On the former principal, clients are disconnected from the database and in-flight transactions are rolled back.

Note

Transactions that have been prepared by using the [!INCLUDEmsCoName] Distributed Transaction Coordinator but are still not committed when a failover occurs are considered aborted after the database has failed over.

See Also

ALTER DATABASE Database Mirroring (Transact-SQL)
Manually Fail Over a Database Mirroring Session (SQL Server Management Studio)
Role Switching During a Database Mirroring Session (SQL Server)