Performance Enhancement of Read-only Transactions Using Speculative Locking Protocol

A read-only transaction (ROT) does not modify any data. The main issues regarding processing ROTs are correctness, data currency and performance. Two-phase Locking (2PL) protocol is widely used for concurrency control with serializabilty as correctness criteria. Even though 2PL processes ROTs correctly with no data currency related issues, the performance deteriorates as data contention increases. To improve the performance, an approach has been proposed in the literature by considering “Snapshot Isolation (SI)” as correctness criteria to process ROTs. At SI-level, ROTs are processed by reading from a snapshot of the committed data and ignoring the modifications produced by the concurrent active transactions. Even though SI-based algorithms improve the performance of ROTs, data currency of ROTs and correctness (serializability) are compromised. In this paper, we propose an approach by extending the notion of speculation to improve the performance of ROTs without compromising data currency of transactions and correctness. Speculation-based approach improves the performance of ROTs by trading extra computing resources without violating serializability as correctness criteria. The simulation results show that with the proposed protocol the throughput performance is improved significantly over 2PL and the data currency of ROTs is improved significantly over SI-based ap proaches with manageable extra resources.