Scheduling transactions in real-time distributed databases

Work on scheduling concurrent transactions in real-time databases must address two issues: (i) synchronization of the corresponding tasks´ accesses to shared data items (ii) guaranteeing timing requirements of the transactions. In this paper, first, we present a concurrency control protocol for real-time databases in a uniprocessor system. In this protocol, we consider the system characteristics to be dynamic. This is in contrast to the priority ceiling protocol and most of the work in scheduling theory where the system workload is assumed to be static and predetermined. Priorities are assigned dynamically to transactions using the well-known strategy Earliest Deadline first. The protocol is proven to avoid deadlocks. The blocking duration arising from mutual exclusion of shared resources is bounded under this protocol. Schedulability analysis for dynamically occurring transactions is provided. Next, we extend the protocol for distributed databases in a shared memory multiprocessor system. The protocol for distributed databases is shown to have the properties of the uniprocessor protocol