Fault-tolerant Applications For The Distributed Multi-tier System Based On Midas

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.