Professional SQL Server™ 2005 Administration

Chapter 17. Database Mirroring

Database mirroring is a software solution for increasing the probability that the database will be available. Database mirroring is a brand new feature in SQL Server 2005. Maximizing the database availability is a top priority for most DBAs. It is hard to explain the pain a DBA goes through when a database goes down; you're unable to get it right back online, and at the same time you're answering pointed questions from your manager. Database mirroring will come to the rescue in certain scenarios, which we explain in this chapter. It will help you get the database back online with automatic or manual failover to your mirror database, adding another alternative to the SQL Server arsenal. In this chapter, we explain the database mirroring concepts, show you how to administer the mirrored database, and give you an example of how to implement database mirroring. We also discuss database snapshot, another brand new feature in SQL Server 2005, which you can use with database mirroring to read the mirrored databases.

Overview of Database Mirroring

Database mirroring is a high-availability solution at the database level, implemented on a per-database basis. To maximize database availability, you need to minimize planned as well as unplanned downtime. Planned downtime is very common, such as changes you have to apply to your production system, hardware upgrades, software upgrades (security patches and service packs), database configuration changes, or database ...