Lock downgrading: An approach to increase inter-transaction parallelism in advanced database applications

Abstract

In this paper, we propose a concurrency control protocol, denoted Cooperative Locking, which extends the two-phase locking protocol by intro- ducing the notion of downgrading of locks proposed in [9]. The basic idea of the proposed protocol is to provide the following functionality: after using an object in a transaction, the user can downgrade a lock on an object to a less restrictive mode before the transaction ends its execution. The prime goal of our proposal is to provide a high degree of inter-transaction parallelism while ensuring serializability of schedules.