Quorum-Based Locking Protocol for Replicas in Object-Based Systems

W e discuss how to lock replicated objects by extending the quorum concept and perform methods o n replicas in a nested invocation. Each method i s issued to a quorum. If a pair of methods are compatible, their quorums may not intersect in our protocol even i f one of the methods is an update type. If a method t is invoked o n multiple replicas and each instance of t invokes another update method U, U is performed multiple times on replicas and then the replicas get inconsistent, i.e. redundant invocation. I n addition, since each instance issues a request to its own quorum, more number of the replicas are locked than the quorum number, i.e. quorum explosion. W e discuss how to resolve the redundant invocations and quorum explosion.