| The development and integration of computer technology and wireless communication technology have realized a brand new computing environment – mobile computing. With mobile computing, people can access data at any time from any location. But there are new challenges for the data transmission, organizing, accessing and management Because of the inherent properties of the mobile environment such as mobility, frequent disconnection, low bandwidth of the wireless network, network heterogeneity, unbalanced network communication, user scalability, limited power etc. So, many concepts on mobile databases have been proposed. The study of mobile database has become a hot spot.Because the wireless mobile communication network is unbalanced and requires good scalability of users, it's suitable to transfer information with the data broadcast method in mobile computing environment. In order to reduce tuning time in the mobile clients, indexes can be added into the broadcast. But the addition of index increases the length of the broadcast message, thus increases the access time of mobile clients. People have made a lot research and put forward many methods of broadcast tuning on reducing accessing time. However, how to optimize both tuning time and accessing time of mobile clients has become a tough researching topic on broadcasting technology. We post a policy that the mobile client establishes broadcast index locally, which can make both tuning time and accessing time in the mobile client optimized.After disconnection, mobile clients execute transactions locally based on the cached data. After reconnection, the transactions in the mobile clients will be submitted as the tentative transactions to the stable hosts to re-execute. Using this method, if there's a high probability of conflicts, the probability of successful submitting of the tentative transactions will be very low. Lots of abortion of tentative transactions will waste server and communication resources, reduce the performance of the whole system. In order to increase success probability for the re-submitting of tentative transactions, we provide a method to submit tentative transactions according to probability and transmit tentative transaction logs in groups. If used in the environments with high conflicting probability, this method can save the costs of transmission on mobile clients, reduce the load on the stable hosts and improve the number of transactions the system can process.In order to improve average responding time, reduce the usage of network bandwidth and improve data availability, mobile clients usually cache part of the data locally. How to keep cache consistent is an important study topic. We use the method based on broadcasting cache invalidating report from the servers to keep cache consistent. We study the mobile client cache consistency in the following three prospects:Many paper have posted the method on periodically broadcasting cache-invalidating reports and promptly broadcasting cache-invalidating reports. We provide a method on broadcasting cache-invalidating reports with variant periods and analyzes its performance and availability.To support offline operations, the invalidating report IRi broadcast from the fixed server at time Ti has to include data collection of ω invalidating report periods before Ti. ( is called invalidating report time window. To use the method to effectively keep cache consistent while the mobile clients disconnect and reconnect frequently, the key point is to select proper value of (. We provide a method to dynamically adjusting invalidating report window (. It theoretically deduces the computing equation for (, analyzes the proper value and implements the method.If the disconnection time of the mobile client is longer than ( broadcasting periods, it can't use invalidating report to keep cache consistent. We provide an array validating method. Although the method often can only locate the range of error pages and can't find the exact page, it isn't the whole cache in the invalidated mobile c...
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