transactionabort

Transaction abort is the termination of a database or transactional system operation before it can be committed. In most database systems, an abort cancels all changes made within the transaction and restores the database to the state it was in at the transaction’s start. The abort event is often treated as a rollback, though some contexts distinguish an explicit abort (initiated by an app or user) from an implicit one (triggered by the system due to errors or conflicts).

Causes of a transaction abort include deadlocks and timeouts, constraint violations, data integrity errors, resource exhaustion, or a system crash. Abort can also occur when an application or administrator explicitly cancels a transaction. In distributed transactions, an abort may occur during two-phase commit if a participant cannot commit or if communication fails, requiring recovery procedures.

Mechanisms and implications: An abort ensures atomicity by ensuring partially completed work is not applied permanently. Most systems perform the undo of changes through logging (undo logs) or equivalent recovery structures. In SQL-based environments, the ROLLBACK command or a rollback to a savepoint achieves an abort. Aborts can impact performance and concurrency, as they may require reattempts or lead to cascading rollbacks.

Recovery and prevention: Robust logging and recovery procedures enable system restoration after an abort or crash. Strategies to reduce abort frequency include appropriate isolation levels, deadlock avoidance or detection, and efficient timeout settings, as well as careful transaction design to minimize long-running operations.

See also: ACID, ROLLBACK, COMMIT, savepoint, deadlock, two-phase commit, crash recovery.