Concurrency control for real-time database systems with mixed transactions

This paper proposes a real-time concurrency control protocol called Reduced Ceiling Protocol (RCP) for database systems consisting of hard and soft real-time transactions. In the RCP, the schedulability of hard real-time transactions is guaranteed by reserving the data items for them and by eliminating the blocking time from soft real-time transactions. Different concurrency control strategies are used to resolve the data conflicts between different combinations of hard and soft real-time transactions. We have shown the characteristics of the schedules generated from the RCP. Simulation experiments have been performed to study the performance of the RCP as compared with the optimistic concurrency control with broadcast commit (OCC-BC). It has been found that the RCP can guarantee the performance of the hard real-time transactions and at the same time reduce the number of deadline missing of the soft real-time transactions.