512 research outputs found

    The embedded operating system project

    Get PDF
    This progress report describes research towards the design and construction of embedded operating systems for real-time advanced aerospace applications. The applications concerned require reliable operating system support that must accommodate networks of computers. The report addresses the problems of constructing such operating systems, the communications media, reconfiguration, consistency and recovery in a distributed system, and the issues of realtime processing. A discussion is included on suitable theoretical foundations for the use of atomic actions to support fault tolerance and data consistency in real-time object-based systems. In particular, this report addresses: atomic actions, fault tolerance, operating system structure, program development, reliability and availability, and networking issues. This document reports the status of various experiments designed and conducted to investigate embedded operating system design issues

    A distribute deadlock detection and resolution algorithm using agents

    Get PDF
    Deadlock is an intrinsic bottleneck in Distributed Real-Time Database Systems (DRTDBS). Deadlock detection and resolution algorithms are important because in DRTDBS, deadlocked transactions are prone to missing deadlines. We propose an Agent Deadlock Detection and Resolution algorithm (ADCombine), a novel framework for distributed deadlock handling using stationary agents, to address the high overhead suffered by current agent-based algorithms. We test a combined deadlock detection and resolution algorithm that enables the Multi Agent System to adjust its execution based on the changing system load, and that selects its victim transactions more judiciously. We demonstrate the advantages of ADCombine over existing algorithms that use agents or traditional edge-chasing through simulation experiments that measure overhead and performance under a widely varying of experimental conditions.deadlockdistribute real-time database systemsdrtdbsalgorithmmulti agent syste

    A unified concurrency control algorithm for distributed database systems

    Get PDF
    We present a unified concurrency-control algorithm for distributed database systems in which each transaction may choose its own concurrency control protocol. Specifically, they integrate two-phase locking, timestamp ordering, and precedence agreement into one unified concurrency-control scheme. They show the correctness of the scheme and study the problem of selecting the best protocol for each transaction to optimize system performance.published_or_final_versio

    Transactors: Unifying Transactions and Actors

    Get PDF
    Composability and deadlock-freedom are important properties that are stated for transactional memory (TM). Commonly, the Semantics of TM requires linearization of transactions. It turns out that linearization of transactions that have cyclic communication brings incomposability and deadlock. Inspired from TM and Actors, this work proposes Transactors that provide facilities of isolation from TM and communication from Actors. We define the semantics of Transactors including support for cyclic transactional communication. An algorithm implementing this semantics is offered. The soundness of the algorithm is proved

    A modified priority based probe algorithm for distributed deadlock detection and resolution

    Full text link

    An adaptive load sensing priority assignment protocol for distributed real-time database systems.

    Get PDF
    Transaction processing in a distributed real time database system (DRTDBS) is coordinated by a concurrency control protocol (CCP). The performance of a CCP is affected by the load condition of a transaction processing system. For example, the performance of the Adaptive Speculative Locking (ASL) protocol degrades in high load conditions of the system. Priority protocols help a CCP by prioritizing transactions. The performance of the priority protocols is also affected by system load conditions, but they can be optimized by dynamically switching between priority protocols at run time when the system load changes. The objective of this research is to develop a protocol, Adaptive Priority Assignment protocol (APAP), which changes the priority protocol at run time to improve the performance of a CCP in a DRTDBS. APAP is implemented in a DRTDBS, where ASL is used as the underlying CCP to validate APAP. The performance of APAP was tested under varying system load conditions with various combinations of the database system parameters. Under the scenarios tested, APAP performed better than other priority protocols and demonstrated that dynamic selection of priority protocols during run time is an effective way to improve the performance of a CCP in a DRTDBS. --Leaf ii.The original print copy of this thesis may be available here: http://wizard.unbc.ca/record=b183575
    • …
    corecore