Speculative Concurrency Control for Real-Time Databases

In this paper, we propose a new class of Concurrency Control Algorithms that is especially suited for real-time database applications. Our approach relies on the use of (potentially) redundant computations to ensure that serializable schedules are found and executed as early as possible, thus, increasing the chances of a timely commitment of transactions with strict timing constraints. Due to its nature, we term our concurrency control algorithms Speculative. The aforementioned description encompasses many algorithms that we call collectively Speculative Concurrency Control (SCC) algorithms. SCC algorithms combine the advantages of both Pessimistic and Optimistic Concurrency Control (PCC and OCC) algorithms, while avoiding their disadvantages. On the one hand, SCC resembles PCC in that conflicts are detected as early as possible, thus making alternative schedules available in a timely fashion in case they are needed. On the other hand, SCC resembles OCC in that it allows conflicting transactions to proceed concurrently, thus avoiding unnecessary delays that may jeopardize their timely commitment

Nested, but Separate: Isolating Unrelated Critical Sections in Real-Time Nested Locking

Prior work has produced multiprocessor real-time locking protocols that ensure asymptotically optimal bounds on priority inversion, that support fine-grained nesting of critical sections, or that are independence-preserving under clustered scheduling. However, while several protocols manage to come with two out of these three desirable features, no protocol to date accomplishes all three. Motivated by this gap in capabilities, this paper introduces the Group Independence-Preserving Protocol (GIPP), the first protocol to support fine-grained nested locking, guarantee a notion of independence preservation for fine-grained nested locking, and ensure asymptotically optimal priority-inversion bounds. As a stepping stone, this paper further presents the Clustered k-Exclusion Independence-Preserving Protocol (CKIP), the first asymptotically optimal independence-preserving k-exclusion lock for clustered scheduling. The GIPP and the CKIP rely on allocation inheritance (a.k.a. migratory priority inheritance) as a key mechanism to accomplish independence preservation

An Evaluation of Network Access Protocols for Distributed Real-time Database Systems

Cataloged from PDF version of article.The results of a considerable number of works addressing various features of real-time database systems (RTDBSs) have recently appeared in the literature. An issue that has not received much attention yet is the performance of the communication network configuration in a distributed RTDBS. In this article, we examine the impact of underlying network architecture on the performance of a distributed RTDBS. In particular, we evaluate the real-time performance of distributed transactions in terms of the fraction of satisfied deadlines under various network access strategies. We also critically examine the common assumption of constant network delay for each communication message exchanged in a distributed RTDBS. (C) 1997 by Elsevier Science Inc

Analysis of concurrency control protocols for real-time database systems

Cataloged from PDF version of article.This paper provides an approximate analytic solution method for evaluating the performance of concurrency control protocols developed for real-time database systems (RTDBSs). Transactions processed in a RTDBS are associated with timing constraints typically in the form of deadlines. The primary consideration in developing a RTDBS concurrency control protocol is the fact that satisfaction of the timing constraints of transactions is as important as maintaining the consistency of the underlying database. The proposed solution method provides the evaluation of the performance of concurrency control protocols in terms of the satisfaction rate of timing constraints. As a case study, a RTDBS concurrency control protocol, called High Priority, is analyzed using the proposed method. The accuracy of the performance results obtained is ascertained via simulation. The solution method is also used to investigate the real-time performance benefits of the High Priority over the ordinary Two-Phase Locking. © 1998 Elsevier Science Inc. All rights reserved

Exploiting Main Memory DBMS Features to Improve Real-Time Concurrency Control Protocols

[No abstract available

Incorporating real-time scheduling methods into database management systems

Many database applications today are characterised by the requirement of timely access to data. This requirement leads to an increasing trend towards adapting real-time scheduling techniques to the management of data access requests. In this paper, we summarise and stimulate developments of time-cognisant scheduling techniques for database management systems. In particular, we review briefly the methods used in mapping timing constraints of transactions into priorities, and the priority-based protocols used for concurrency control. We also suggest useful directions for future research

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

\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