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What is primary replica in AlwaysOn?
The primary replica makes the primary databases available for read-write connections from clients. The primary replica sends transaction log records of each primary database to every secondary database. This process – known as data synchronization – occurs at the database level.
How does always on Replication work?
This is a new HA/DR feature in SQL 2012 and combines best of failover clustering and database mirroring. It allows you to create a group of databases which failover together as a unit from one replica/instance of SQL Server to another replica/instance of SQL Server in the same availability group.
Can a secondary replica be added to an availability group?
If you have never added any availability replica to an availability group, see the “Server instances” and “Availability groups and replicas” sections in Prerequisites, Restrictions, and Recommendations for Always On Availability Groups (SQL Server). You must be connected to the server instance that hosts the current primary replica.
How to create a secondary replica in azure?
The Add Azure Replica Wizard only supports virtual machines created with the Classic deployment model. New Virtual Machine deployments should use the newer Resource Manager model. If you are using Virtual Machines with Resource Manager, then you must manually add the secondary Azure replica using Transact-SQL commands (not shown here).
Can you create read replicas in different regions?
You can create a read replica in a different region from your primary server. Cross-region replication can be helpful for scenarios like disaster recovery planning or bringing data closer to your users. Basic tier servers only support same-region replication. You can have a primary server in any Azure Database for PostgreSQL region.
Can a replica go back to the old primary server?
If you promote a replica to be the primary server, you cannot establish replication back to the old primary server. If you want to go back to the old primary region, you can either establish a new replica server with a new name (or) delete the old primary and create a replica using the old primary name.