INTEGRATED CONCURRENCY-CONTROL PROTOCOL FOR HARD REAL-TIME DATABASE-SYSTEMS

Real-time transactions must meet their deadlines in hard real-time dat abase systems (RTDBS). To preserve data integrity, hard RTDBS require concurrency control protocols to synchronise transactions to access sh ared data. Transaction blocking enforced by concurrency control protoc ols leads to priority inversion problems which violate the principle o f priority-based scheduling and degrade system schedulability. Unfortu nately, this blocking time can be indefinitely long, which is unaccept able in hard real-time applications. An integrated scheduling and conc urrency control protocol is proposed that allows a high priority trans action to pre-empt an uncommitted lower priority transaction while pre venting the lower priority transaction from being restarted even in th e face of data conflicts. The new protocol alleviates priority inversi on problems by allowing more transaction schedules than other protocol s.