The rapid explosion in the use of wireless devices, combined with the simultaneous infrastructure expansion required to suport a massive number of users, has made ubiquitous access to data a reality. When a large number of users simultaneously accesses global data in a mobile computing environment, an efficient means to manage a large amount of concurrent transactions is required. Current multi‐database concurrency control schemes do not address the limited bandwidth and frequent disconnections associated with wireless networks. This article describes a new hierarchical concurrency control algorithm, v‐lock, that addresses the shortcomings of existing multi‐database concurrency control schemes. The algorithm uses global locking tables created with semantic informantion contained within a hierarchy to serialize global transactions, and remove global deadlocks. Additionally, wireless transmission of data is subject to weak or frequent disconnection. With the increased amount of local memory available at the mobile unit, data replication can be used to provide local data availability, limiting the restrictions imposed by a wireless mobile environment. In a mobile, multi‐database environment, local autonomy restrictions prevent the use of a page‐or‐file‐based data replication scheme. This article describes a new data replication scheme to address to limited bandwidth and local autonomy restrictions. Consistency is maintained by using a parity‐based invalidation scheme of data cached at the mobile unit. Additionally, a simple prefetching scheme is used to further improve the effectiveness of the proposed scheme. Finally, simulated results of the concurrency control and replication algorithms are presented and discussed.

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In a mobile environment, the result of queries often depends on the client's location. These queries are called location dependent queries (LDQ). Applying the concept of caching to LDQs provides a means for efficient processing when queries exhibit both semantic similarity and spatial locality. Existing LDQ caching schemes require database (DB) servers to provide validity regions (VR) for LDQ results, which introduces significant processing and/or storage overhead. As a result, DB servers may only provide the validity information conditionally or do not provide it at all. We propose a novel LDQ proxy scheme that can estimate the VR if DB servers do not provide such information. The simulation results show that the LDQ proxy reduces both the LDQ response time and the database workload.