A Log-Based Cache Consistency Control of Spatial Databases in Mobile Computing Environments

摘要

In mobile client/server computing environments, mobile clients make access to their server to get interested data and then are disconnected because of high cost of wireless communication. Mobile clients usually keep their own local copies in order to reduce the overhead of communicating with the server. The updates of the server database sometimes are subject to leading to invalidation of the cached map in mobile clients. However it is not efficient to resend the entirely copied map from the server to mobile clients for solving invalidation. This paper proposes a log-based update propagation method to propagate the server's update into its corresponding mobile clients by sending only update logs. The log-based update propagation scheme raises new issues as follows. First, the continuously growing of update logs downgrades the speed of searching for the relevant log data for a specific client. Second, there is considerable overhead of transmitting the update logs into mobile clients by using wireless communication. To solve these problems, we define unnecessary logs and then suggest methods to remove the unnecessary logs.