Integrated concurrency control protocol for hard real-time database systems

Real-time transactions must meet their deadlines in hard real-time database systems (RTDBS). To preserve data integrity, hard RTDBS require concurrency control protocols to synchronise transactions to access shared data. Transaction blocking enforced by concurrency control protocols leads to priority inversion problems which violate the principle of priority-based scheduling and degrade system schedulability. Unfortunately, this blocking time can be indefinitely long, which is unacceptable in hard real-time applications. An integrated scheduling and concurrency control protocol is proposed that allows a high priority transaction to pre-empt an uncommitted lower priority transaction while preventing the lower priority transaction from being restarted even in the face of data conflicts. The new protocol alleviates priority inversion problems by allowing more transaction schedules than other protocols.