Maintaining consistency in mobile systems /
In the client-server based systems, data is cached at clients
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1997.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=736580071&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | In the client-server based systems, data is cached at clients to improve the performance. When data items are updated at the server, inconsistency arises among these copies. Main taining consistency is one of the major issues in these systems. This problem is more complicated in mobile systems because of the low bandwidth and asymmetric wireless channels, and the mobile and resource poor clients. The objective of this research is to study various issues associated with maintaining consistency in the mobile systems. In some applications, the wireless channels are treated as one-way broadcast channels to improve the scalability. In these channels, the clients do not send requests to the server. The server continuously broadcasts the data over the channel. The clients listen to the channel and access the required data whenever it is broadcast. To improve the performance, the clients cache data. Consistency problems arise when the data is updated at the server. Two schemes , immediate propagation scheme and invalidation scheme, are used in the traditional systems. The performance of these schemes in the one-way broadcast channels is analyzed. Many other issues arise while using these schemes in this environment. Some of these issues, like missing updates, effect on the tuning time and tolerating communication errors, are discussed. The mobility of clients is another parameter that affects consistency and performance in distributed systems. In distributed systems, data is often replicated at multiple servers. Data copies at these servers are periodically synchronized to reduce the communication overhead. But, in a mobile system, a client often moves from place to place. If the servers are not in consistent state, it has to access from the previous server, which incurs a high communication cost. An optimal period of synchronization which depends on the mobility rate of clients is calculated. Similarly, various schemes that are used to improve the data access time of a mobile client are analyzed. |
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| Item Description: | Vita. "Major Subject: Computer Science". |
| Physical Description: | xi, 88 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 65-71. |