In a database mirroring configuration, the server instance on which the mirror database resides. The copy of the database that is typically fully synchronized with the principal database. The database mirroring session operates synchronously and, optionally, uses a witness, as well as the principal server and mirror server.Ī failover initiated by the database owner, while the principal server is still running, that transfers service from the principal database to the mirror database while they are in a synchronized state. The only form of role switching is forced service (with possible data loss). The database mirroring session operates asynchronously and uses only the principal server and mirror server. The two server instances (the principal server or the mirror server) that act as role-switching partners for a mirrored database.Ī failover initiated by the database owner upon the failure of the principal server that transfers service to the mirror database while it is in an unknown state. The process by which, when the principal server becomes unavailable, the mirror server to take over the role of principal server and brings its copy of the database online as the principal database. For more information, see Upgrading Mirrored Instances.
#Fabriwin part mirroring upgrade
This form of upgrade is known as a rolling upgrade. This will incur the downtime of only a single failover. To minimize downtime for a mirrored database, you can sequentially upgrade the instances of SQL Server that are hosting the failover partners. Improves the availability of the production database during upgrades. For more information, see Automatic Page Repair (Availability Groups: Database Mirroring).
If this request succeeds, the unreadable page is replaced by the copy, which usually resolves the error. The partner that is unable to read a page requests a fresh copy from the other partner. For more information, see Operating Modes, later in this topic.Ī database mirroring partner running on SQL Server 2008 Enterprise or later versions automatically tries to resolve certain types of errors that prevent reading a data page. For more information, see Role Switching, later in this topic.ĭatabase mirroring provides complete or almost complete redundancy of the data, depending on whether the operating mode is high-safety or high-performance. In the other operating modes, the database administrator has the alternative of forcing service (with possible data loss) to the standby copy of the database. In the event of a disaster, in high-safety mode with automatic failover, failover quickly brings the standby copy of the database online (without data loss). Benefits of Database Mirroringĭatabase mirroring is a simple strategy that offers the following benefits: For information about support for database mirroring, restrictions, prerequisites, recommendations for configuring partner servers, and recommendations for deploying database mirroring, see Prerequisites, Restrictions, and Recommendations for Database Mirroring.
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