two-phase commit


two-phase commit

(database)A technique for maintaining integrity indistributed databases. Where a system uses two or moredatabase, a transaction among the distibuted database shouldbe atomic ("all or nothing"). This is done by handling thetransaction in two phases. First the databases prepare thetransaction, confirm that it is possible to process it, andlock the relevant record.

Once all the required databases confirm that the transactionis viable, the system instructs them all to commit it -i.e. to make it permanent. If it is not possible to processit, the system will instruct the databases to rollback(undo) the transaction.

two-phase commit

A technique for ensuring that a transaction successfully updates all appropriate files in a distributed database environment. All DBMSs involved in the transaction first confirm that the transaction has been received and is recoverable (stored on disk). Then each DBMS is told to commit the transaction (do the actual updating).

Traditionally, two-phase-commit meant updating databases in two or more servers, but the term is also applied to updating two or more different databases within the same server. See transaction, transaction file and transaction processing.