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Data & Analytics · Advanced

Always On Availability Groups (AG)

A SQL Server high-availability and disaster-recovery feature that replicates a group of databases to secondary replicas with automatic or manual failover.

Definition

An availability group has one primary and up to eight secondary replicas, each in synchronous or asynchronous commit mode. Secondaries can serve read-only queries and backups. A listener provides a stable connection name across failovers. Availability groups replicate at the database level and run on top of Windows Server Failover Clustering or Pacemaker.

Exam tip

Availability groups protect databases and allow readable secondaries; a Failover Cluster Instance protects the whole instance using shared storage.

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