Summary form only given. Data caching is an effective way of improving system performance. This is especially crucial in mobile databases because of the limited bandwidth and slower communication speed of wireless channels. In this paper we present a data caching algorithm, referred to as HDC (hot data caching), and compare its performance with LRU (least recently used) cache replacement scheme through simulation.

Recent advances in mobile computing and wireless communication have enabled the deployment of broadcast based information systems such as, wireless internet, traffic information, etc. The users and research community have recognized its potential for meeting the growing information demands of the future. At present existing systems are mainly pull-based (on-demand) and their performance highly depends on the broadcast schedule they use. Previous studies in on-demand scheduling have focused mainly on single item requests to keep the investigation simple. However, scheduling algorithms for single item request are unable to manage efficiently multi-item requests which are becoming more common. In addition to this these more and more requests are becoming transactional in nature. In this paper we take into consideration these requirements and study scheduling problems arising in on-demand broadcast environment and propose an efficient algorithm. We report its performance and demonstrate that our algorithm successfully manage multi-item simple and transactional requests and significantly reduces the wait time, tuning time and avoids transaction aborts.

We propose an concurrency control mechanism (CCM) for mobile database systems (MDS) that ensures epsilon serializability and report its performance.

We present a transaction commit protocol, "Transaction Commit On Timeout (TCOT)," based on a "timeout" approach for Mobile Database Systems (MDS), which can be universally used to reach a final transaction termination decision (e.g., commit, abort, etc.) in any message-oriented system. Particularly suited for a wireless environment, a timeout mechanism is the only way to minimize the impact of the slow and unreliable wireless link. We compare TCOT to a modified version of 2PC to show its superiority based on commit time.