In Database technologies, a rollback is an operation which returns the database to some previous state. Rollbacks are important for database integrity, because they mean that the database can be restored to a clean copy even after erroneous operations are performed. They are crucial for recovering from database server crashes; by rolling back any transaction which was active at the time of the crash, the database is restored to a consistent state.

In SQL, ROLLBACK is a command that causes all data changes since the last Begin work (SQL), or Start transaction (SQL) to be discarded by the relational database management system (RDBMS), so that the state of the data is rolled back to the way it was before those changes were made.

A ROLLBACK statement will also release any existing Savepoints that may be in use.

In most SQL dialects, ROLLBACKs are connection specific. This means that if two connections are made to the same database, a ROLLBACK made in one connection will not affect any other connections. This is vital for proper Concurrent programming.

The rollback feature is usually implemented with a Database_log, but can also be implemented via multiversion concurrency control.

=See also=

*Savepoint

=External links=