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SQL Server Always On is a high-availability and disaster-recovery solution that provides an enterprise-level alternative to database mirroring. Introduced in SQL Server 2012, Always On Availability Groups maximizes the availability of a set of user databases for an enterprise. Here, we are going to delve into how you can ensure high availability of your data with SQL Server Always On.
Setting up SQL Server Always On
To start, we need to define the Availability Groups (AGs), which are container entities for a set of databases, dispatchers and listeners to resources, meant to be failed over together for high availability and disaster recovery. Here’s an example of how to create an AG:
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-- Start a New Availability Group Session CREATE AVAILABILITY GROUP [YourAG] WITH (AUTOMATED_BACKUP_PREFERENCE = PRIMARY) FOR DATABASE [YourDB] REPLICA ON N'YourServer' WITH (ENDPOINT_URL = N'tcp://YourServer:5022', FAILOVER_MODE = AUTOMATIC, AVAILABILITY_MODE = SYNCHRONOUS_COMMIT, BACKUP_PRIORITY = 50, SECONDARY_ROLE(ALLOW_CONNECTIONS = NO)); |
This script will create an automated backup preference for your server. You will need to replace ‘YourAG’, ‘YourDB’, and ‘YourServer’ with the respective titles used in your server.
Accessing your Data
Once your servers are up and running, you can access your data using the SQL Server Management Studio or any application that can access SQL Server. Let’s write a query to select all data from a specified table:
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USE [YourDB]; GO SELECT * FROM [YourTable]; |
Again, replace ‘YourDB’ and ‘YourTable’ with your database and table name respectively. This SQL script uses the USE keyword to switch to your target database and then selects all data from the target table.
Conclusion
Always On Availability Groups is a powerful feature that provides high availability for your SQL Server databases. Its ease of use, flexibility, and seamless integration into the SQL Server system makes it an ideal choice for many businesses with high data availability requirements. While the setup and management require a comprehensive understanding of the SQL Server system as a whole, the benefits are worth the investment.