"subtransactionwas" - 1 õppematerjal

IT arhitektuur

For a transaction to be started there must not be an ongoing transaction. Nested ·The objective of having subtransactions is to be able to set save points within a transaction in order to revert to these save points. ­If an unreconcileable inconsistency is reached, it then becomes possible to undo only a part rather than the whole transaction by aborting only the subtransaction that caused the inconsistency. ­The parent transaction then continous at the point where the aborted subtransactionwas started. ·To start a subtransaction, transactional clients invoke a begin transaction operation from the transaction coordinator during the course of a parent transaction. ·With nested transactions it is, therefore, permitted to have a begin transaction operation without having completed the previous transaction and such a begin will launch a subtransaction. ·Subtransactionscan have subtransactionsof their own, leading to an arbitrary deep nesting hierarchy.