Maintaining Temporal Consistency in Real-Time Database Systems

A real-time database system usually requires maintaining a large amount of temporal data objects which record and model a physical, real-world environment. These temporal data objects are accessed by application transactions to generate the ultimate control actions. In the actual applications, real-time database systems require not only ensuring transactions finished in the specified time limits (deadlines), but also guaranteeing temporal consistency of data objects accessed by transactions. The traditional real-time concurrency control protocols stress on meeting transaction deadlines, while ignore the fact that transactions require reading fresh and consistent data. In this paper, we first give the formal definitions of temporal consistency about data and transaction. Then, we present a novel realtime concurrency control protocol called TCHP-2PL (temporal consistency high priority 2 phase lock), which can guarantee temporal consistency. Further, in order to obtain the better real-time performance, an enhanced TCHP-2PL called STCHP-2PL is proposed by introducing the concept of similarity. Performance tests show that the STCHP-2PL can still ensure the very well real-time performance under circumstances of guaranteeing temporal consistency.