What is SQL AlwaysOn?

AlwaysOn is an integrated high-availability (HA) and disaster recovery (DR) solution that provides redundancy within a SQL Server data center. It allows fast application failover during both scheduled and unplanned downtime.

What is the purpose of availability groups in the SQL environment?

Introduced in SQL Server 2012 (11. x), Always On availability groups maximizes the availability of a set of user databases for an enterprise. An availability group supports a failover environment for a discrete set of user databases, known as availability databases, that fail over together.

Does SQL AlwaysOn require clustering?

SQL Server Always On is a flexible design solution to provide high availability (HA) and disaster recovery (DR). It is built upon the Windows Failover Cluster, but we do not require the shared storage between the failover cluster nodes.

What is database availability group?

A database availability group (DAG) is a set of up to 16 Exchange Mailbox servers that provides automatic, database-level recovery from a database, server, or network failure. DAGs use continuous replication and a subset of Windows failover clustering technologies to provide high availability and site resilience.

What is SYS partitions in SQL Server?

Contains a row for each partition of all the tables and most types of indexes in the database. Special index types such as Full-Text, Spatial, and XML are not included in this view. All tables and indexes in SQL Server contain at least one partition, whether or not they are explicitly partitioned. Column name.

How many databases can you have in an availability group?

There is as such no limit defined. Microsoft has tested only upto 10 AG and 100 Databases. If you want to create more AGS, You will have to do so and test the workload you have to see that you do not land into performance issues for same.

Does SQL always require quorum?

The quorum for Always On availability groups is based on all nodes in the WSFC regardless of whether a given cluster node hosts any availability replicas. In contrast to database mirroring, there is no witness role in Always On availability groups.

What is DAC in exchange?

Datacenter Activation Coordination (DAC) mode is a property of a database availability group (DAG). DAC mode is disabled by default but should be enabled for all DAGs with two or more members that use continuous replication.