Rollback (data management)
Encyclopedia
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.
The rollback feature is usually implemented with a transaction log, but can also be implemented via multiversion concurrency control
.
Practical database recovery techniques guarantee cascadeless rollback, therefore a cascading rollback is not a desirable result.
,
(RDBMS), so that the state of the data is "rolled back" to the way it was before those changes were made.
A
s that may be in use.
In most SQL dialects,
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
technologies, a rollback is an operation which returns the database to some previous state. Rollbacks are important for database integrity
Data integrity
Data Integrity in its broadest meaning refers to the trustworthiness of system resources over their entire life cycle. In more analytic terms, it is "the representational faithfulness of information to the true state of the object that the information represents, where representational faithfulness...
, 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
Database transaction
A transaction comprises a unit of work performed within a database management system against a database, and treated in a coherent and reliable way independent of other transactions...
which 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 via multiversion concurrency control
Multiversion concurrency control
Multiversion concurrency control , in the database field of computer science, is a concurrency control method commonly used by database management systems to provide concurrent access to the database and in programming languages to implement transactional memory.For instance, a database will...
.
Cascading rollback
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.
SQL
In SQLSQL
SQL is a programming language designed for managing data in relational database management systems ....
,
ROLLBACK is a command that causes all data changes since the last BEGIN WORK, or START TRANSACTION to be discarded by the relational database management systemRelational database management system
A relational database management system is a database management system that is based on the relational model as introduced by E. F. Codd. Most popular databases currently in use are based on the relational database model....
(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 savepointSavepoint
A savepoint is a way of implementing subtransactions within a relational database management system by indicating a point within a transaction that can be "rolled back to" without affecting any work done in the transaction before the savepoint was created. Multiple savepoints can exist within a...
s 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 concurrency.See also
- SavepointSavepointA savepoint is a way of implementing subtransactions within a relational database management system by indicating a point within a transaction that can be "rolled back to" without affecting any work done in the transaction before the savepoint was created. Multiple savepoints can exist within a...
- CommitCommit (data management)In the context of computer science and data management, commit refers to the idea of making a set of tentative changes permanent. A popular usage is at the end of a transaction. A commit is an act of committing.-Data management:...
- Norton GhostGhost (software)Ghost is a disk cloning program product sold by Symantec. Originally developed by Murray Haszard in 1995 for Binary Research, the technology was acquired in 1998 by Symantec. The name Ghost is an acronym for General Hardware-Oriented System Transfer.- History :Binary Research developed Ghost in...
- UndoUndoUndo is a command in many computer programs. It erases the last change done to the document reverting it to an older state. In some more advanced programs such as graphic processing, undo will negate the last command done to the file being edited....