Replication is a powerful feature in SQL Server that allows you to distribute data across multiple servers. However, making schema changes to tables involved in replication can be challenging. In this article, we will discuss the steps to make schema changes in SQL Server replication without dropping the entire publication.

Step 1: Prepare for the Changes

Before making any schema changes, it is important to prepare your database and ensure that replication commands are distributed and there are no pending replication tasks. To do this, follow these steps:

1. Stop any users from connecting to the database. You can put the database in DBO only mode or perform these procedures after hours when usage is lightest.
2. Make sure all pending replication commands are distributed. If you are using continuous replication, it should only take a few seconds for them to post to your subscriber.
3. Stop replication for the database. You can do this by going to Replication Monitor in Enterprise Manager, locating your publication, and stopping the Log Reader Agent and Distribution Agent.
4. Drop all subscriptions using the sp_dropsubscription stored procedure.

Step 2: Make the Schema Changes

Once you have prepared your database, you can proceed with making the schema changes. Follow these steps:

1. Make the necessary schema changes on the publisher. Keep in mind that if you are adding or dropping a column that will be part of the article, you will need to make the same changes on all subscribers.
2. Create a new article using the sp_addarticle stored procedure. Make sure to include any vertical or horizontal filters that were used before.
3. Add the subscribers back to the publication using the sp_addsubscription stored procedure.
4. Test the replication by inserting and deleting a row in each modified table. Start the Log Reader and Distribution Agents and check if the commands replicate successfully.

Step 3: Finalize the Changes

Once you have tested the replication and ensured that the changes are working correctly, you can finalize the process. Follow these steps:

1. Take the database out of DBO only mode.
2. Apply the changes to your production database.

It is important to have a backup plan in case something goes wrong. You can either restore from a backup and try again or execute a new snapshot to resync all the subscribers.

Remember, it is recommended to set up a test database and mirror the publication you want to change before applying the changes to your production database. This will allow you to work through the process and build your scripts until they work correctly.

By following these steps, you can make schema changes in SQL Server replication without dropping the entire publication. This will help you efficiently manage your replication environment and keep your data synchronized across multiple servers.