A locking protocol for object-oriented database systems (OODBSs) is presented. The protocol can exploit the semantics of methods invoked on encapsulated objects. Compared to conventional page-oriented or record-oriented concurrency control protocols, the proposed protocol greatly improves the possible concurrency because commutative method executions on the same object are not considered as a conflict. An OODBS application example is presented. The principle of open-nested transactions is reviewed. It is shown that, using the locking protocol in an open-nested transaction, the locks of a subtransaction are released when the subtransaction completes, and only a semantic lock is held further by the parent of the subtransaction.>

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Multi-level transactions have received considerable attention as a framework for high-performance concurrency control methods. An inherent property of multi-level transactions is the need for compensating actions, since state-based recovery methods do no longer work correctly for transaction undo. The resulting requirement of operation logging adds to the complexity of crash recovery. In addition, multi-level recovery algorithms have to take into account that high-level actions are not necessarily atomic, e.g., if multiple pages are updated in a single action.