What is "rollback"

In database technologies, a rollback (reversal) is an operation that returns the database to a previous state. Rollbacks are important for database integrity because it means that the database can be restored to a clean copy even after erroneous operations are performed. They are crucial for recovering database server crashes; reversing any transaction that was active at the time of the crash, the database is restored to a consistent state.

The Rollback feature is usually implemented with a transaction log, but can also be implemented through multiversion competition control.