Run and Hit: Optimistic concurrency control for mobile computing

Limitation of bandwidth, restriction of resources, and frequent disconnection are the main characteristics of mobile computing environments. To reduce these problems, a new form of data delivery was proposed in which the server broadcasts data to mobile hosts that listen to the broadcast channel. In this paper, we propose an optimistic concurrency control scheme, called RaH (Run and Hit) based on the broadcast invalidation report. In our scheme a transaction performs (Runs) its operation without conflict checks until the server broadcasts (Hits) an invalidation report. When a mobile host catches an invalidation report, it checks whether or not the transaction in the mobile host has accessed conflicting data items. Our scheme achieves high transaction throughput because transactions that have accessed read-write conflicting data items can be committed by use of re-ordering. For re-ordering, the server maintains only one time-stamp per data item. By simulation experiments we show that our scheme consistently demonstrates excellent performance with low space overhead in all parameter settings.