Integrating standard transactions in firm real-time database systems

Real-time database systems are designed to handle workloads where transactions have completion deadlines and the goal is to meet these deadlines. However, many real-time database environments are characterized by workloads that are a mix of real-time and standard (non-real-time) transactions. Unfortunately, the system policies used to meet the performance goals of real-time transactions often work poorly for standard transactions. In particular, optimistic concurrency control algorithms are recommended for real-time transactions, whereas locking-based protocols are suited for standard transactions. In this paper, we present a new database system architecture in which realtime transactions use optimistic concurrency control and, simultaneously, standard transactions use locking. We prove that our architecture maintains data integrity and show, through a simulation study, that it provides significantly improved performance for the standard transactions without diminishing the real-time transaction performance. We also show, more generally, that the proposed architecture correctly supports the co-existence of any group of concurrency control algorithms that adhere to a standard interface.