What is Transactional Replication in SQL Server and how to setup?

What is Transactional Replication in SQL Server?

Transactional replication is a SQL Server feature. It copies data from one database, known as the publisher, to another, called the subscriber. The data is synchronized in near real-time. This feature is suitable for scenarios with frequent updates. Subscribers need the most recent changes.

Key Components of Transactional Replication

1. Publisher: The source database that holds the original data.
2. Distributor: A server or database that manages the replication process, storing metadata and transactions before forwarding them to subscribers.
3. Subscriber: The destination database that receives the replicated data.
4. Publication: A collection of database objects (tables, views, etc.) to replicate.
5. Subscription: The link between the publication and the subscriber.

Steps to Set Up Transactional Replication

1. Prepare the Environment

• Ensure SQL Server Agent is running on the Publisher, Distributor, and Subscriber servers.
• Confirm that the publisher and subscriber databases are compatible with transactional replication.
• Verify network connectivity between the servers.

2. Configure the Distributor

The distributor can be on the publisher or a separate server.

1. Open SQL Server Management Studio (SSMS).
2. Right-click on the Replication folder and select Configure Distribution.
3. Follow the wizard to:
   • Choose the distributor (local or remote).
   • Specify the distribution database name and location.
   • Configure the distribution snapshot folder (a shared folder accessible to all nodes).

3. Create a Publication

1. In SSMS, expand the Replication folder at the publisher.
2. Right-click Local Publications and choose New Publication.
3. Select the database you want to publish.
4. Choose Transactional Publication.
5. Select the articles (tables, views, or stored procedures) to replicate.
6. Configure filtering (optional):
   • You can filter rows or columns if only part of the data is needed by subscribers.
7. Specify the snapshot agent settings:
   • The snapshot is the initial copy of the data sent to subscribers.
8. Complete the wizard and optionally script the actions for later use.

4. Create a Subscription

1. In SSMS, expand the Replication folder at the subscriber.
2. Right-click Local Subscriptions and choose New Subscription.
3. In the wizard:
   • Connect to the publisher and select the publication.
   • Specify the subscriber server and database.
   • Choose the subscription type:
     • Push Subscription: The publisher pushes changes to the subscriber.
     • Pull Subscription: The subscriber pulls changes from the publisher.
   • Configure the subscription schedule for synchronization.
   • Set the security settings for the agent.

5. Start the Snapshot Agent

1. At the publisher, expand the Replication folder > Local Publications.
2. Right-click the publication and select View Snapshot Agent Status.
3. Start the Snapshot Agent to generate the initial snapshot for subscribers.

6. Monitor and Verify Replication

1. Use SSMS replication monitoring tools:
   • Check the status of the distributor, publisher, and subscriber.
   • Monitor agent jobs to ensure they are running successfully.
2. Test the replication:
   • Insert, update, or delete data in the publisher database and confirm that changes appear in the subscriber database.

Advantages of Transactional Replication

• Near real-time synchronization of data.
• Suitable for read-heavy workloads on subscribers.
• Allows selective replication of objects and data.
• Minimal impact on publisher performance compared to other replication types.

Common Use Cases

• Reporting databases that require up-to-date data.
• Distributing data across geographically distributed systems.
• Synchronizing data between production and backup systems.

Troubleshooting Tips

• Check SQL Server Agent logs for errors.
• Use the Replication Monitor for real-time status.
• Ensure permissions are correctly configured for snapshot and log reader agents.
• Verify network stability between servers.

By following these steps, transactional replication can be efficiently set up to maintain synchronized data across systems.