Indatabase technologies, arollback is an operation which returns the database to some previous state. Rollbacks are important for databaseintegrity, because they mean that the database can be restored to a clean copy even after erroneous operations are performed.^[1] They are crucial for recovering from database server crashes; by rolling back anytransaction which was active at the time of the crash, the database is restored to a consistent state.

The rollback feature is usually implemented with atransaction log, but can also be implemented viamultiversion concurrency control.

A cascading rollback occurs in database systems when a transaction (T1) causes a failure and a rollback must be performed. Other transactions dependent on T1's actions must also be rollbacked due to T1's failure, thus causing a cascading effect. That is, one transaction's failure causes many to fail.

Practical database recovery techniques guarantee cascadeless rollback, therefore a cascading rollback is not a desirable result. Cascading rollback is scheduled by dba.

SQL refers to Structured Query Language, a kind of language used to access, update and manipulate database.InSQL,ROLLBACK is a command that causes all data changes since the lastSTART TRANSACTION orBEGIN to be discarded by therelational database management systems (RDBMS), so that the state of the data is "rolled back" to the way it was before those changes were made.^[2]

AROLLBACK statement will also release any existingsavepoints 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, aROLLBACK made in one connection will not affect any other connections. This is vital for properconcurrency.

Rollbacks are not exclusive to databases: anystatefuldistributed system may use rollback operations to maintainconsistency. Examples of distributed systems that can support rollbacks includemessage queues andworkflow management systems. More generally, any operation that resets a system to its previous state before another operation or series of operations can be viewed as a rollback.

• Savepoint
• Commit
• Undo
• Schema migration

• Ramez Elmasri (2007).Fundamentals of Database Systems.Pearson Addison Wesley.ISBN 978-0-321-36957-4.
• "ROLLBACK Transaction", Microsoft SQL Server.
• "Sql Commands", MySQL.

• Database theory
• Transaction processing
• Reversible computing
• Database management systems

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