A distributed database for SAMS on a set of networked personal computers

Pao Yue-kong Library Electronic Theses Database

A distributed database for SAMS on a set of networked personal computers


Author: Mok, Sui-kei
Title: A distributed database for SAMS on a set of networked personal computers
Degree: M.Sc.
Year: 1999
Subject: Distributed databases
Database management
School management and organization -- Data processing
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Computing
Pages: viii, 68 leaves : ill. ; 31 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1460532
URI: http://theses.lib.polyu.edu.hk/handle/200/2463
Abstract: SAMS was the first computer system developed by the Government to assist the administrative and management works of the primary and secondary schools in Hong Kong. Limited by the original design and the choice of the development platform, SAMS had a lot of drawbacks. For example, the centralized database model had lowered the system accessibility and availability. In addition by restricting the system in a central location within the school premise did not abide to the working habits of the ever-changing conditions. Furthermore, the primitive 'file locking' had lead to a low system response time. Motivated by the drawbacks considered, a distributed database model was proposed. The study had proposed a database model which was a combination of the two key issues in distributed database theory: data replication and data partitioning. For example, in the processing of students' academic results, SAMS used a single table SAASSSCO.DBF to record all the students' subject marks. In the distributed database model, SAASSSCO.DBF is group-partitioned into 5 smaller tables: F1AASSSCO.DBF to F5AASSSCO.DBF. The grouping criterion was according to the form levels, i.e., F.1 to F.5. As there was not a best allocation algorithm available (actually this was a NP complete problem), the study had performed an experiment to determine the optimum data replication scheme for the proposed database model. Results indicated that by replicating 3 tables in each workstation's harddisk would be a best allocation scheme for the experimental conditions considered. The percentage gain in the Average Job Completion Time was over 26%. In addition, the standard deviation of the Average Job Completion Time decreased when the number of replica increased. When the data were further divided into different form levels, it revealed that 2 replica would favor F.4 and F.5 's assessment processing. In general, larger number of replica should be employed when the file size was large. The study, however, had only considered a single module of SAMS. The effects of the interaction between the different modules should be subject to further studies. Finally, the study had advocated a reengineering of SAMS. The platform of the workstation should be upgraded to Windows NT Workstation. In addition, the system should consider the latest development in distributed database theory such as dynamic load balancing so that it would suit the ever changing IT environment in schools.

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