A Hybrid Distributed Optimistic Concurrency Control Methodfor High-Performance Real-Time Transaction Processing

The conventional lock scheme tends to suffer from a cascade of blockings, whilethe optimistic concurrency control (OCC) scheme may suer from wasting resources. To over-come these problems, some researchers have proposed a combination of OCC and lock in trans-action processing. Using this method, Thomasian proposed the hybrid method for conventional distributed transaction processing, and Lam proposed the DOCC-DA protocol for distributed real-time database system based on forward validation. This paper proposes a new protocol, called Hybrid Distributed Optimistic Concurrency Control Embedded in two-Phase Commit, which is based on back validation. The new protocol makes use of access invariance and runtime information which can guarantee a rerun transaction to meet its deadline and abort the fruitless runtransactions as early as possible. A series of simulation experiments have been done to investigate the performance of the new protocol. The results show that its performance is consistently better than that of other protocols.