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SQL Server 2008: Administration in Action by Rod Colledge

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11.5. Failover options

The three types of failover options are automatic, manual, and forced service. Table 11.2 summarizes the availability of these options based on the mirroring mode and presence of a witness instance.

Table 11.2. Supported failover modes by mirroring type 
Mirroring modeWitnessSupported failover modes
High performanceNoForced service
High safetyNoManual or forced service
High safetyYesAutomatic, manual, or forced service

Let's begin this section with a look at automatic failover.

11.5.1. Automatic failover with SNAC

If the principal instance fails, automatic failover brings the mirror database online as the new principal database. For this to occur, all of the following conditions must be true:

  • Mirroring must be operating in ...

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