OBSERVATIONS ON OPTIMISTIC CONCURRENCY CONTROL SCHEMES

Attstraet-Gptimistic concurrency control schemes allow uncontrolled access to shared data objects during transaction processing under the explicit assumption that read and write coticts among transactions are rare events. Before a transaction commits, the DBMS has to validate that no conflict has occurred Conflict resolution mainly relies on transaction abort. Two different optimistic concurrency control schemes are introduced and compared to each other. The problems of implementing such schemes and their implications on DBMS processing is investigated in some detail. A number of general properties of optimistic concurrency control schemes is derived, and their advantages and drawbacks w.r.t. two-phase locking approaches are discussed.