Transaction processing in a mobile, multi-database environment

Current distributed and multi-database systems are designed to allow timely and reliable access to large amounts of data distributed at different loca tions. Changes in current technology now allow users to access this data vi a a wide variety of devices through a diverse communication medium. A mobil e data access system is an environment in which a wireless-mobile computing environment is superimposed upon a multi-database environment in order to realize "anywhere, anytime" access capability. As a potentially large numbe r of users may siultaneously access the available data, there are several i ssues involved in the ability to concurrently manage transactions. Current multi-database concurrency control schemes do not efficiently manage these accesses because they do not address the limited bandwidth and frequent dis connections associated with wireless networks. This paper first introduces the so-called mobile data access system (MDAS) and then proposes a new hierarchical concurrency control algorithm. The pro posed concurrency control algorithm, v-lock, uses global locking tables cre ated with semantic information contained within the hierarchy. The locking tables are subsequently used to serialize global transactions, and detect a nd remove global deadlocks. The performance of the new algorithm is simulat ed and the results are presented. In addition (through simulation) the perf ormance of the proposed algorithm has been compared and contrasted against the site graph method, the potential conflict graph method, and the forced conflict method.