A Step-by-Step Guide: Adding a New Database to the Availability Group

Downtime can lead to significant financial losses, reputational damage, and frustrated users. SQL Server’s Always On Availability Groups (AGs) offer a robust solution by maintaining synchronous or asynchronous replicas of your primary database, allowing for seamless failover in case of an outage. But what if you need to add a new database to an existing AG? This blog post dives deep into the process of adding a new database to the availability group, empowering you to seamlessly integrate new databases into your high availability infrastructure.

Understanding Availability Groups and Prerequisites:

An AG consists of a primary replica, which holds the active database, and one or more secondary replicas that maintain a synchronized copy. This ensures that if the primary replica becomes unavailable, a secondary can swiftly assume the role, minimizing downtime and data loss.

However, adding a new database to an AG isn’t as simple as creating it. The database must adhere to specific prerequisites:

• Recovery Model: Set to FULL to enable transaction log backups, crucial for maintaining replica consistency.
• Auto-Close: Disabled, ensuring the database remains available for continuous replication.
• Read-Write Mode: Enabled, allowing modifications on both primary and secondary replicas.
• User Database: Only user databases are eligible for AGs. System databases are excluded.
• Backup Availability: A full backup of the new database is essential for various seeding methods.

Read More: MS SQL Server Database Backup and Recovery

Adding a New Database to the Availability Group

There are two primary methods for adding a new database to your AG:

1) The Add Database to Availability Group Wizard

This user-friendly wizard streamlines the process, making it ideal for beginners. Here’s how it works:

1. Connect to the server hosting the primary replica using SQL Server Management Studio (SSMS).
2. Navigate to Always On High Availability > Availability Groups > Availability Databases in Object Explorer.

3. Right, Click on the ‘Availability Databases’ => Click on ‘Add Database…’

4. You will get a ‘Select Databases’ window with the databases name, check the box with the databases name which you are going to add in the ‘Availability Group’ and click on ‘Next’.

5. You will get a ‘Connect to Replicas’ window where you have to connect to Existing Replicas as shown below with credentials.

6. In the ‘Select Initial Data Synchronization’ step, you have to select the appropriate preference of data synchronization. In our environment, we have selected the ‘Join only’ option because we already restored the full and transactional log backups.

NOTE: We selected ‘Join only’ because we already took full and log backup of the database from the primary node and then restored those backups to the secondary server.

Seeding Methods:

• Automatic Seeding (Recommended): Utilizes the log stream transport to efficiently transfer transactions from the primary to the secondary replicas, minimizing downtime. However, it requires configuring endpoints for communication.
• Manual Seeding: Provides more control but involves manually restoring a full backup of the database on each secondary replica. This method is often used when automatic seeding isn’t feasible due to network constraints or complex configurations. (Adding a New Database to the Availability Group)

For more information on ‘Data Synchronization’, pls check here…

7. In the ‘Validation’ step, it will show the errors if any. Click on ‘Next’…

8. On the ‘Summary’ page, it will show you the summary. If all is ok, then click on ‘Finish’…

9. After adding the databases in the ‘Availability Group’, you will get the message ‘The wizard completed successfully.’

Check the databases sync status on the ‘Dashboard’.

2) Using the Availability Group Properties Dialog:

This method offers granular control over the addition process. Follow these steps:

• Connect to the server hosting the primary replica using SSMS.
• Navigate to Always On High Availability > Availability Groups in Object Explorer.
• Right-click on the desired AG and select Properties.
• In the Availability Group Properties dialog, go to the Availability Databases tab.
• Click Add and enter the name of the new database.
• Configure additional options like seeding method and synchronization.

Advanced Considerations:

While the above methods provide a solid foundation, there are additional considerations for seasoned users:

• Availability Mode: Choose between synchronous and asynchronous replication depending on your desired data consistency level and performance trade-offs.
• Redistribution Queue Size: Adjust the size based on the expected workload and anticipated data transfer volume.
• Synchronization Health: Monitor the synchronization status of the new database to ensure data consistency across replicas. (Adding a New Database to the Availability Group)

Post-Addition Tasks:

Once the new database is successfully added to the AG, crucial steps remain:

• Validate the configuration: Verify that the new database is listed in the Availability Databases pane of the AG properties.
• Monitor synchronization: Ensure efficient data transfer between replicas using tools like SQL Server Management Studio or AlwaysOn Health PowerShell cmdlets.
• Test failover (optional): Conduct controlled failover scenarios to test the functionality and readiness of your AG in a simulated outage.

Conclusion:

By understanding and applying the methods outlined above, you can effectively add new databases to your existing Availability Group, enhancing the resilience and scalability of your data infrastructure. Remember, consulting the official Microsoft documentation for specific version details and advanced configuration options is always recommended.

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