Supporting predictability in real-time database systems

Real-time database systems (RTDBSs) have timing constraints in their specifications, such as read times, deadlines and other temporal constraints. In addition, RTDBSs must adapt to changes in the operating environment and guarantee the completion of critical transactions. Previous research efforts in RTDBSs have been focused on scheduling transactions with soft or firm deadlines with serializability as the sole correctness criterion. Few results have been reported for supporting predictable transaction execution and guaranteeing the temporal consistency of data. The goal has been to minimize the deadline miss ratio and to maintain the logical consistency of data. In this paper, we address the issues of predictability and temporal consistency in RTDBSs. We briefly discuss the characteristics and requirements of RTDBSs, and present a transaction processing scheme that supports multiple levels of predictability for real-time transactions. The performance of the proposed scheme and the cost of achieving a high level of predictability is studied by using simulation.