What is READ COMMITTED?

READ COMMITTED is SQL Server's default transaction isolation level. It prevents dirty reads by ensuring a statement does not read uncommitted changes.

With the traditional locking implementation, readers generally use shared locks and may wait for incompatible writers. When READ_COMMITTED_SNAPSHOT is enabled for the database, READ COMMITTED can instead use row versions for many reads, reducing reader-writer blocking.

Therefore, knowing the database option is important when diagnosing concurrency behavior.