Moderate Concurrency Control in Distributed Object Systems

Objects are concurrently manipulated by multiple transactions in object-based systems. We newly introduce availability and exclusion types of conflicting relations among methods. Then, we define a partially ordered relation on lock modes showing which modes are stronger than others. We newly propose a moderate locking (ML) protocol. Here, an object is initially locked in a weaker mode than an intrinsic mode of the method. Then, the lock mode is escalated to the method mode. The weaker the initial mode is, the higher concurrency is obtained but the more frequently deadlock occurs. The ML protocol is evaluated in terms of throughput and deadlock compared with the pessimistic and optimistic locking protocol.