A Study On Strategies For Caching Consistency Maintenance Of Mobile Database

With the rapid development and promotion of computer technology and mobile communications technology, more and more portable mobile devices can be linked with network for communication freely at anytime and anywhere. As a result, it is how to access any data at anytime and anywhere that has become the key point of the study on mobile database, which has been one of the current research hotspots. As for the frequent connection and disconnection of network as well as the bandwidth asymmetry, the employment of cache technology and data broadcast technology can improve the data access performance and the scalability of the whole system. Meanwhile, connected or disconnected operation can be finished by client, which can raise the reliability of mobile data. Combining cache technology and data broadcast technology, cache invalidation report has been proved to be one of the classic strategies for cache consistency maintenance.Based on the combination of cache technology and data broadcast, invalidation report serves as one of the cache consistency maintenance strategies, which works in the following way:the server updates the data invalidation report through down-link broadcast, according to which the client can maintain the cache consistency. Traditionally, the study on invalidation report focus on its model and its broadcasting mechanism, without consideration of how to improve the granularity of invalidation report according to the size, access and update frequency of the data.Through the overview of the former study on cache invalidation report, this thesis will propose dynamic cache invalidation report to maintain the cache consistency based on the traditional model. This strategy put forward evaluation function, according to which weights can be obtained. In other words, taking the access frequency, update frequency, size, and access latency into consideration, the weights can be worked out through the function, based on which invalidation reports with different granularity will be presented for different data items and in turn different broadcasting strategies can be employed in different reports.Simulated experiment has been implemented, the results of which has proved that the dynamic cache invalidation report can adapt to the qualities of mobile network and it is superior to the traditional model both in throughput of the system and the use ratio of bandwidth...