A study of two transaction-processing architectures for distributed real-time database systems

Cataloged from PDF version of article.A real-time data base system (RTDBS) is designed to provide timely response to the transactions of data-intensive applications. Processing a transaction in a distributed RTDBS environment presents the design choice of how to provide access to remote data referenced by the transaction. Satisfaction of the timing constraints of transactions should be the primary factor to be considered in scheduling accesses to remote data. In this article, we describe and analyze two different alternative approaches to this fundamental design decision. With the first alternative, transaction operations are executed at the sites where required data pages reside. The other alternative is based on transmitting data pages wherever they are needed. Although the latter approach is characterized by large message volumes carrying data pages, it is shown in our experiments to perform better than the other approach under most of the work loads and system configurations tested. The performance metric used in the evaluations is the fraction of transactions that satisfy their timing constraints. © 1995

Pricing of Information Services Using Real-Time Databases: A Framework for Integrating User Preferences and Real-Time Workload (Best Paper Runner Up)

Many revolutionary information products are being offered or envisioned in electronic commerce setting. Since an economic paradigm and mass customization are implicit in electronic commerce, these products must be produced and delivered at appropriate prices with user desired service characteristics such as response time, correctness, and completeness. In this research, we investigate the information services pricing with response time (or delay) as the only service characteristic since response time can implicitly characterize other quality attributes such as correctness. In order to recognize customers’ preferences, real-time databases, where transaction processing is time-cognizant, are central to information providers and can be thought of as “manufacturers” of customized products. We propose to capture user preferences by a priority pricing mechanism based on economic theory. This pricing is concerned with database access and is independent of content pricing. Our approach has a natural overload1 management and admission control2 techniques that can potentially increase collective benefits. Our model is evaluated using simulation and is shown to outperform a system without access pricing mechanism with respect to both system wide benefits and RTDB performance

A study of two transaction-processing architectures for distributed real-time data base systems

A real-time data base system (RTDBS) is designed to provide timely response to the transactions of data-intensive applications. Processing a transaction in a distributed RTDBS environment presents the design choice of how to provide access to remote data referenced by the transaction. Satisfaction of the timing constraints of transactions should be the primary factor to be considered in scheduling accesses to remote data. In this article, we describe and analyze two different alternative approaches to this fundamental design decision. With the first alternative, transaction operations are executed at the sites where required data pages reside. The other alternative is based on transmitting data pages wherever they are needed. Although the latter approach is characterized by large message volumes carrying data pages, it is shown in our experiments to perform better than the other approach under most of the work loads and system configurations tested. The performance metric used in the evaluations is the fraction of transactions that satisfy their timing constraints. © 1995

Processing real-time transactions in a replicated database system

A database system supporting a real-time application has to provide real-time information to the executing transactions. Each real-time transaction is associated with a timing constraint, typically in the form of a deadline. It is difficult to satisfy all timing constraints due to the consistency requirements of the underlying database. In scheduling the transactions it is aimed to process as many transactions as possible within their deadlines. Replicated database systems possess desirable features for real-time applications, such as a high level of data availability, and potentially improved response time for queries. On the other hand, multiple copy updates lead to a considerable overhead due to the communication required among the data sites holding the copies. In this paper, we investigate the impact of storing multiple copies of data on satisfying the timing constraints of real-time transactions. A detailed performance model of a distributed database system is employed in evaluating the effects of various workload parameters and design alternatives on the system performance. The performance is expressed in terms of the fraction of satisfied transaction deadlines. A comparison of several real-time concurrency control protocols, which are based on different approaches in involving timing constraints of transactions in scheduling, is also provided in performance experiments. © 1994 Kluwer Academic Publishers

\u3cem\u3eRTC\u3c/em\u3e: Language Support for Real-Time Concurrency

This paper presents language constructs for the expression of timing and concurrency requirements in distributed real-time programs. Our programming paradigm combines an object-based paradigm for the specification of shared resources, and a distributed transaction-based paradigm for the specification of application processes. Resources provide abstract views of shared system entities, such as devices and data structures. Each resource has a state and defines a set of actions that can be invoked by processes to examine or change its state. A resource also specifies scheduling constraints on the execution of its actions to ensure the maintenance of its state\u27s consistency. Processes access resources by invoking actions and express precedence, consistency. Processes access resources by invoking actions and express precedence, consistency and timing constraints on action invocations. The implementation of our language constructs with real-time scheduling and locking for concurrency control is also described

Multiclass Query Scheduling in Real-Time Database Systems

In recent years, a demand for real-time systems that can manipulate large amounts of shared data has led to the emer-gence of real-time database systems (RTDBS) as a research area. This paper focuses on the problem of scheduling queries in RTDBSs. We introduce and evaluate a new algorithm called Priority Adaptation Query Resource Scheduling (PAQRS) for handling both single class and multiclass query workloads. The performance objective of the algorithm is to minimize the number of missed deadlines, while at the same time ensuring that any deadline misses are scattered across the different classes according to an administratively-defined miss distribution. This objective is achieved by dynamically adapting the system’s admission, mem-ory allocation, and priority assignment policies according to its current resource configuration and workload characteristics. A series of experiments confirms that PAQRS is very effective for real-time query scheduling

A comparative study of transaction management services in multidatabase heterogeneous systems

Multidatabases are being actively researched as a relatively new area in which many aspects are not yet fully understood. This area of transaction management in multidatabase systems still has many unresolved problems. The problem areas which this dissertation addresses are classification of multidatabase systems, global concurrency control, correctness criterion in a multidatabase environment, global deadlock detection, atomic commitment and crash recovery. A core group of research addressing these problems was identified and studied. The dissertation contributes to the multidatabase transaction management topic by introducing an alternative classification method for such multiple database systems; assessing existing research into transaction management schemes and based on this assessment, proposes a transaction processing model founded on the optimal properties of transaction management identified during the course of this research.ComputingM. Sc. (Computer Science