Research issues in real-time database systems

Cataloged from PDF version of article.Today's real-time systems are characterized by managing large volumes of data. Efficient database management algorithms for accessing and manipulating data are required to satisfy timing constraints of supported applications. Real-time database systems involve a new research area investigating possible ways of applying database systems technology to real-time systems. Management of real-time information through a database system requires the integration of concepts from both real-time systems and database systems. Some new criteria need to be developed to involve timing constraints of real-time applications in many database systems design issues, such as transaction/query processing, data buffering, CPU, and IO scheduling. In this paper, a basic understanding of the issues in real-time database systems is provided and the research efforts in this area are introduced. Different approaches to various problems of real-time database systems are briefly described, and possible future research directions are discussed

Transaction processing in distributed active real-time database systems

An active real-time database system (ARTDBS) is designed to provide timely response to the critical situations that are defined on database states. Although a number of studies have already addressed various issues in ARTDBSs, little attention has been paid to scheduling transactions in a distributed ARTDBS environment. In this paper, 2 we describe a detailed performance model of a distributed ARTDBS and investigate various performance issues in time-cognizant transaction processing in ARTDBSs. The experiments conducted evaluate the performance under various types of active workload and different distributed transaction-processing architectures. The performance metric used in the evaluations is the fraction of transactions that violate their timing constraints. We also describe and evaluate a nested transaction execution scheme that improves the real-time performance under high levels of active workload. © 1998 Elsevier Science Inc. All rights reserved

Research issues in real-time database systems. Survey paper

Today's real-time systems are characterized by managing large volumes of data. Efficient database management algorithms for accessing and manipulating data are required to satisfy timing constraints of supported applications. Real-time database systems involve a new research area investigating possible ways of applying database systems technology to real-time systems. Management of real-time information through a database system requires the integration of concepts from both real-time systems and database systems. Some new criteria need to be developed to involve timing constraints of real-time applications in many database systems design issues, such as transaction/query processing, data buffering, CPU, and IO scheduling. In this paper, a basic understanding of the issues in real-time database systems is provided and the research efforts in this area are introduced. Different approaches to various problems of real-time database systems are briefly described, and possible future research directions are discussed. © 1995

Real-time transaction scheduling in database systems

A database system supporting a real-time application, which can be called "a real-time database system (RTDBS)", has to provide real-time information to the executing transactions. Each RTDB transaction is associated with a timing constraint, usually in the form of a deadline. Efficient resource scheduling algorithms and concurrency control protocols are required to schedule the transactions so as to satisfy both timing constraints and data consistency requirements. In this paper,† † An earlier version of this paper was published in the Proceedings of ACM Computer Science Conference '92. we concentrate on the concurrency control problem in RTDBSs. Our work has two basic goals: real-time performance evaluation of existing concurrency control approaches in RTDBSs, and proposing new concurrency control protocols with improved performance. One of the new protocols is locking-based, and it prevents the priority inversion problem‡ by scheduling the data lock requests based on prioritizing data items. The second new protocol extends the basic timestamp-ordering method by involving real-time priorities of transactions in the timestamp assignment procedure. Performance of the protocols is evaluated through simulations by using a detailed model of a single-site RTDBS. The relative performance of the protocols is examined as a function of transaction load, data contention (which is determined by a number of system parameters) and resource contention. The protocols are also tested under various real-time transaction processing environments. The performance of the proposed protocols appears to be good, especially under conditions of high transaction load and high data contention. © 1994

Priority inheritance in soft real-time databases

Due to resource sharing among tasks, priority inversion can occur during priority-driven preemptive scheduling. In this work, we investigate solutions to the priority inversion problem in a soft real-time database environment where two-phhse locking is employed for concurrency control. We examine two basic schemes for addressing the priority inversion problem, one based on priority inheritance and the other based on priority abort. We also study a new scheme, called conditional priority inheritance, which attempts to capitalize on the advantages of each of the two basic schemes. In contrast with previous results obtained in real-time operating systems, our performance studies, conducted on an actual real-time database testbed, indicate that the basic priority inheritance protocol is inappropriate for solving the priority inversion problem in real-time database systems. We identify the reasons for this performance. We also show that the conditional priority inheritance scheme and the priority abort scheme perform well for a wide range of system workloads