SQL Interview: 48 Enabling RCSI for a database

This is a post in the SQL Interview series. These aren’t trick or gotcha questions, they’re just questions designed to scope out a candidate’s knowledge around SQL Server and Azure SQL Database.

Section: Administrator Level: Medium

Question:

Your database application has been suffering from signficant blocking issues.

One developer has suggested enabling RCSI for the database.

If you do that, what’s different about how the database would operate?

What code changes are needed to use it?

Answer:

When you enable RCSI (read committed snapshot isolation), SQL Server automatically changes the isolation level for any read committed reads, to read committed snapshot reads.

No code changes are required but you need to make sure the application works ok with the altered behavior. Most applications do not depend on the standard blocking behavior of read committed, but it is possible that they do.

2025-05-16