What is AlwaysOn Availability Groups and what is this technology used for?

AlwaysOn Availability Groups is a high availability and disaster recovery technology in Microsoft SQL Server. It allows creating groups of databases that are synchronized across multiple SQL Server instances (replicas). The main purpose is to ensure continuous application operation and minimize downtime during failures.

Key features:

• Support for multiple secondary replicas for reading and backup.
• Automatic failover between replicas.
• Replication at the database group level, not individual databases.

Example of use: In a large system with critical data, AlwaysOn allows having a primary database and several secondary ones, which can be used for reading or quickly switching in case of primary failure.