Lock-free hybrid concurrency control strategy for mobile environment

Concurrency control is one of the most important components of transaction management, which ensures the correctness of shared data items. Most of the existing concurrency control techniques use locking mechanism to achieve concurrency control, which leads to transaction starvation and deadlock. On the other hand, the non-locking techniques (i.e. optimistic and timestamp ordering) are associated with high abortion rate and excessive transaction restart. This paper presents a lock-free hybrid concurrency control strategy that combines the features of optimistic and timestamp-ordering strategies. The technique allows mobile devices to freely read data items and allowed to pre-commit while in disconnection mode, and latter propagate the pre-committed data during reconnection for global commitment. A designed hybrid concurrency simulator (HCsim) was used to evaluate the performance of the new scheme using transaction abortion rate and response time as performance metrics. Simulation results have shown that lock-free hybrid strategy outperform both optimistic and timestamp strategies in terms of minimizing the transaction abortion rate and response time.