基于Agent的容灾系统数据同步机制

容灾系统可以有效的降低各单位通过计算机管理企业数据所产生的潜在风险,而在容灾系统的建设当中,数据同步问题是其中一个较难解决的问题.为实现异构型数据库之间的数据同步,本文提出了一种基于Agent技术的远程数据同步实现方案.该方案有效运用了Agent的特有属性,可以独立于具体的异构数据库,实现跨平台的数据同步:能够灵活配置,可在对系统性能影响较小的情况下,充分满足企业级数据的同步要求.     

基于主从异步复制技术的容灾实时系统研究与实现

介绍了一个实用的容灾实时系统SDP_R．为提高系统的性能，SDP_R采用严格的主从异步复制技术和多线程技术．实验表明，多线程技术和多进程技术能够较大地提高系统的性能，而且相比多进程技术，多线程技术所需的内存要少得多．详细探讨了采用多线程技术时怎样保证数据的一致性．SDP_R系统不仅满足容灾系统设计准则，而且与Oracle以及Informix等数据库提供商提供的数据复制技术相比，SDP_R通过数据库底层函数层可以屏蔽不同数据库产品或版本之间的差异，从而实现不同数据库产品和版本之间的数据复制．SDP_R适用于使用多种数据库产品或版本的系统，如智能网系统．同时，SDP_R系统可以处理数据拷贝图为任意拓扑结构的情况．容灾系统SDP_R已经实现，它是下一代智能网分布式SDP中的一个主要功能模块．     

远程应用级容灾系统架构设计与研究

应用级容灾系统能够在灾难中最大限度地保障计算机信息系统提供正常的服务，如何构建远程应用级容灾系统是计算机信息系统中的重要课题。详细分析了应用级容灾系统的基础理论，剖析了容灾系统的系统结构模型，容灾系统的具体实施模型，对远程应用级容灾系统设计与实现进行了详细的研究。     

数据异地容灾的实现

日益增长的信息量必然发生大量的数据传输、存储和数据交换,数据安全成为影响整个信息系统的一个重要因素为了应付区域性灾害,如地震、海啸、战争等因素导致多个机房同时损毁,数据永久性丢失,其它如区域性的病毒泛滥、蓄意破坏、严重误操作等人为因素也可能导致同城备份中心失效。建立一套异地数据备份系统已经成为信息系统建设的必要组成部分,会成为保证数据安全的最后一道防线。本文详细阐述了某信息系统数据异地容灾的实现。     

电信支撑系统容灾解决方案

随着电信运营商之间的竞争越来越激烈,业务连续性要求对电信运营商IT支撑系统的容灾建设提出了更高标准。本文对容灾解决方案涉及的数据复制、网络切换、时间同步和容灾中心选址等问题进行讨论,推荐了几种较优的解决方案。     

浅析中小企业数据容灾理论和技术

文中系统地分析了企业数据容灾的理论和技术。介绍建立一个容灾备份系统,首先要了解容灾备份的等级要求和评价指标,其次要了解其具体实现技术。最后对容灾系统的关键技术进行了分析和讨论。     

一种针对SAN构架企业的异地数据容灾系统设计方法

设计了一种针对SAN构架企业的异地数据容灾系统。该系统针对SAN构架的特性,将企业数据按特征划分为静态数据和动态数据。基于电子链接的方法论标准进行企业异地数据容灾系统的设计,通过虚拟磁带库的备份、传输及恢复,结合更改流程控制方法实现静态数据的异地容灾;通过对标准异步数据复制方式创新改进,实现动态数据的异地容灾,同时提高了复制效率,降低了链路最高带宽要求。更好的体现了系统的可靠性与经济性。     

远程异步数据复制系统的设计与实现

远程数据复制技术是远程容灾系统的核心技术,在保持两地间数据一致性和实现灾难恢复中起到关键作用。该文在研究远程数据复制技术的基础上,设计并实现了基于存储设备级的远程异步数据复制系统。系统不占用主机系统资源,对上层的文件系统和应用程序透明,可以降低上层软件设计的复杂程度。     

建设容灾系统的几点思考

本文结合目前容灾建设的实际情况，对各种容灾实现方案进行对比，分析不同方案的利弊和适用范围，以及保证容灾建设成功的关键条件等进行了论述，对容灾系统建设能起到一定的借鉴作用．     

在CORBA中实现异步调用

介绍了CORBA中的四种异步激发方式：多线程方式、单向异步激发方式、延迟同步激发方式以及异步方法调用方式,并讨论了各种异步激发方式的优缺点。     

Asynchronous multicaches

In previous multicache consistency mechanisms, processors have been required to synchronize with all caches when updating shared data. This synchronization occurs while invalidating inconsistent copies of the data. We present a simple cache consistency mechanism which demonstrates that this synchronization is unnecessary. In particular, we show that it is possible to buffer invalidation requests at the caches while guaranteeing that concurrent programs are correctly executed by the system. This offers increased processor utilization by allowing the caches to handle invalidation requests between accesses by their associated processors. In addition, buffering invalidation requests offers greater utilization of shared memory by speeding up store operations. Additional contributions of this paper are the development of a formal definition of consistency and of a technique for proving that a system is consistent. Geoffrey M. Brown is currently an Assistant Professor of Electrical Engineering at Cornell University, Ithaca, NY. His research interest include distributed systems, and formal methods for hardware design. Dr. Brown received the B.S. degree in engineering from Swarthmore College in 1982, M.S. degree in electrical engineering from Stanford University in 1983, and Ph. D. degree in electrical engineering from the University of Texas at Austin in 1987. He was employed by Motorola Semiconductor during 1983–1984.     

异步系统功能模块的设计基础

异步系统的研究是当前SOC系统设计领域的热点,异步系统通过握手协议代替了传统同步系统中的全局时钟,以此来保证时序和通信并有效的减少了功耗。在异步系统中,各个模块都可以有各自的本地时钟,它们可根据需求关闭自己的本地时钟。模块与模块之间采用握手协议实现通信。本文将对异步系统功能模块的设计作介绍,并且结合一个例子使读者对异步系统有所了解。     

Surface and deep learning processes in distance education: Synchronous versus asynchronous systems

Distance learning is different from regular learning in the classroom. One of the main factors which influence the effectiveness of the learning process is the interaction that exists between the teacher and the student. Our research indicates that different interactions have different effects.     

采用异步技术动态显示服务器当前系统时间

文章介绍采用异步技术在客户端Web页面上动态显示服务器当前系统时间的方法。在客户端每隔一时间间隔通过XML-HttpRequest对象向服务器发出异步请求,获取并显示服务器系统时钟的当前时间。在服务器端采用异步页面模式由一线程来产生基于系统时钟的当前时间,而接受客户端请求的组件则可直接读出该时间并返回客户端。     

Asynchronous Forward-checking for DisCSPs

A new search algorithm for solving distributed constraint satisfaction problems (DisCSPs) is presented. Agents assign variables sequentially, but perform forward checking asynchronously. The asynchronous forward-checking algorithm (AFC) is a distributed search algorithm that keeps one consistent partial assignment at all times. Forward checking is performed by sending copies of the partial assignment to all unassigned agents concurrently. The algorithm is described in detail and its correctness proven. The sequential assignment method of AFC leads naturally to dynamic ordering of agents during search. Several ordering heuristics are presented. The three best heuristics are evaluated and shown to improve the performance of AFC with static order by a large factor. An experimental comparison of AFC to asynchronous backtracking (ABT) on randomly generated DisCSPs is also presented. AFC with ordering heuristics outperforms ABT by a large factor on the harder instances of random DisCSPs. These results hold for two measures of performance: number of non-concurrent constraints checks and number of messages sent. Research supported by the Lynn and William Frankel Center for Computer Sciences and the Paul Ivanier Center for Robotics and Production Management.     

Asynchronous Schwarz methods applied to constrained mechanical structures in grid environment

This paper deals with the parallel solution of the stationary obstacle problem with convection–diffusion operator. The obstacle problem can be formulated by various ways and in the present study it is formulated like a multivalued problem. Another formulation by complementary problem is also considered. Appropriate discretization schemes are considered for the numerical solution on decentralised memory machines by using parallel synchronous and asynchronous Schwarz alternating algorithms. The considered discretization schemes ensure the convergence of the parallel synchronous or asynchronous Schwarz alternating methods on one hand for the solution of the multivalued problem and on the other hand for the solution of the complementary problem. Finally the implementation of the algorithms is described and the results of parallel simulations are presented.     

异步电动机的建模仿真方法研究

随着我国经济的不断发展,我国的各种工业都在不断发展,工厂数量也在不断的增加,这样电动机就成为了工厂发展的重要影响因素之一,众所周知,电动机是工厂内最普遍和最重要的电气设备,电动机运行的是否稳定也影响着工厂工作是否顺利,但是在异步电动机的运行过程中也存在着一些不足问题,例如异步电动机“存在的”的问题,异步电动机“存在的”是指系统的电量过低或者是电压过低,导致电量无法与机器顺利联通,导致电动机工作运行出现问题,这样就会给电动机设备带来很大程度的损坏,电动机一旦发生“存在的”问题,就会给工厂的运行带来很大的不便,包括很大的经济损失。因此,本人就电动机的建模仿真方法为基础,进行一些分析,并最终提出一些可行性的建议。