Priority-based speculative locking protocols for distributed real-time database systems

In recent years, a number of concurrency control protocols have been proposed to improve performance within Distributed Real Time Database Systems. Speculative Locking (SL) allows parallelism and execution of multiple instances of conflicting transactions to improve performance in Distributed Database Systems. This research extends SL by proposing two concurrency control protocols: Preemptive Speculative Locking (PSL), and Priority Inheritance Speculative Locking (PiSL). PSL allows preemption and abortion of lower priority transactions when conflict occurs, whereas PiSL allows the lower priority transaction to inherit the priority of the blocked transaction and continue execution. Using a distributed real-time transaction processing simulator that supports nested transaction model, an extensive set of experiments have been conducted which demonstrate that both PSL and PiSL outperform SL. Among the two proposed protocols, PSL performs better when data contention and system load are high. The performance metrics include number of transactions that meet their deadlines, and resource utilization.