A middleware for improving concurrency of long running transactions

Transaction management in different application contexts is still a challenging task. In this paper we propose a novel method in order to improve concurrency of a particular kind of transaction, known as long running transactions. Differently from other techniques presented in the literature, we design a sort of hybrid approach between optimistic and pessimistic concurrency models. From one hand, our basic idea consists in taking into account frequent disconnections or inactivity periods of a generic transaction during its life-cycle and, from the other one, we consider the semantics related to operations produced by transactions. Our solution avoid an indefinite or long resource locking due to disconnecting (or idle) transactions or a high rate of preventive aborts; eventually, a transaction semantic compatibility is exploited in order to increase the concurrency of reconcilable operations on the same resources. To these purposes, we have implemented a middleware with the aims of emulating a transactional scheduling, and several experiments have been carried out.