Towards Unifying Database Scheduling and Concurrency Control: A Frontier Approach

Real-time databases have numerous applications, including commodities trading, military command and control, patient monitoring, air tra c control, and exible manufacturing. All of these applications require that data be processed in such a way that the data and output of the database remains logically consistent . They also require that deadlines imposed on database operations are met (temporal consistency) . Thus, the ultimate goal of scheduling and concurrency control for real-time databases is to maintain both temporal and logical consistency of the transactions and of the data. In situations, such as overload, where both temporal consistency and logical consistency cannot be met, a transaction scheduler may have to sacri ce one requirement for the other and make a trade-o between the two. For example, suppose that a transaction tread is reading some sensor data in a real-time database, and another transaction, tupdate, needs to update that data in order to maintain the temporal consistency of the data and/or the transaction. If tupdate were allowed to execute, the logical consistency of tread would be violated, but if tupdate were blocked, the temporal consistency of the sensor data or of tupdate could be violated. Thus, one requirement must be traded-o for the other.