基于MIDAS的分布式多层系统的容错研究与应用

【作者】 王志刚；

【导师】 刘宏； 陈传淼；

【作者基本信息】 湖南师范大学 ， 计算数学， 2001， 硕士

【摘要】 随着网络技术与网络应用的发展，分布式计算与分布式数据库的应用也越来越受到人们的重视，并得到了许多厂商的大力支持。一批有关多层分布式系统控制的协议、中间件和标准也在涌现并趋于成熟，为数据库的应用开辟了新的空间，多层分布式应用结构开始被国内用户广泛采纳。Borland公司在Delphi中推出的MIDAS标准，对多层分布式结构又赋予了更深的内涵。由于分布式多层系统可以将不同或相同的工作分散放在网络上的不同机器上运行，故即使有10％的机器出了问题，系统还可以以接近90％的整体性能运行。分布式应用能解决一般C/S方式无法解决的问题，并将在Internet/Intranet、电子商务等领域获得广泛的应用。 本文介绍了多层分布式系统的一般原理、及相关思想、概念和技术。结合Delohi的MIDAS(Multi-Tier Distributed Application Services Suite)探讨了多层分布式系统的结构以及多层分布式数据库应用的工作模型。也对基于CORBA的系统进行了简介。在第三章研究了基于MIDAS的多层分布式系统数据存取原理以及MIDAS控制的各事件处理函数之间的关系，并为正确掌握数据的存取和更新提供了方法。 基于多层分布式系统的关键技术之一是容错问题，如果一个分布式系统解决不好这个问题，则分布式系统是完全没有什么价值的，本文在最后一章较深入地研究了MIDAS下多层分布式系统的容错方案，并结合MIDAS的两个重要部件TSimpleObjectBroker和TClientDataSet给出了一些容错算法，通过继承TclientDataSet类，创建了一个克服了TClientDataSet存在问题的新类TZTClientDataSet，保留了原来的功能，增加了新的方法。最后用一个例子介绍了新类的应用。更多还原

【Abstract】 With the development of network technology and network applications,distributed computation and distributed database applications are got more and more attentions and supported by many vendors. Some protocals, middle components and standards about distributed system are made and becoming mature. The distributed systems have more advantages over C/S systems, especially on multi-tier distributed system area. A distributed system could do the work that the client/server systems could not complete. A distributed system is higher reliability than non- distributed system. By distributing the workload over many machines,if 10 percent of machines are down at any moment, the system should be able to continue to work with a 10 percent loss in performance. So the multi-tier distributed system will be adopted by Internet/Intranet applications, including E-commerces.In this paper, I will introduce the principles, concepts and technology of the multi-tier distributed system. Using the MIDAS of delphi 5,1 will discuss the construction of a multi-tier distributed system and the model of a database application based on multi-tier distributed system. I also point out the principles of the multi-tier distributed system based on CORE A .One of the key questions about multi-tier distributed system is fault tolerance. If fault tolerance could not be solved well, the multi-tier distributed system could not work reliably . So I will mainly discuss the fault tolerance technology. Finally I will give some methods about solving fault tolerance.更多还原