A transaction execution model for mobile computing environments

Abstract

A mobile computing environment is characterized by limited execution capability at the mobile hosts, low bandwidth and the relatively high costs of wireless connection, and frequent disconnections and mobility of the mobile hosts. Such an environment naturally suggests an optimistic mode of execution, where the mobile host caches data and does the computation in disconnected mode and, on reconnection, the transaction is either committed or aborted based on the current values in the fixed network. -- We propose a new transaction execution model, based on optimistic concurrency control mechanism, which dynamically adjusts the transaction execution status at the mobile host to be consistent with the database state on the mobile support station. This increases the possibility of the transaction to commit successfully and hence makes the computation on the mobile host more meaningful. A detailed algorithm is presented and its adaptability to various aspects of the mobile environment discussed. -- We further strengthen the computation at the mobile host by facilitating partial guarantee against invalidation. This is accomplished by using a flexible concurrency control scheme which integrates optimistic and pessimistic approaches to access data items based on Read/Write and Write/Write-conflicts. -- Keywords: Mobile computing; Transaction processing; Concurrency control; Optimistic approach; Re-execution.