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Replicated systems that run over partitionable environments, can exhibit increased availability if isolated partitions are allowed to optimistically continue their execution independently. This availability gain is traded against consistency, since several replicas of the same objects could be updated separately. Once partitioning terminates, divergences in(More)
The Hidra Membership Monitor (HMM) is a distributed service that maintains the current set of active nodes in a cluster of machines. This protocol allows the detection of multiple machine joins or failures in a unique reconfigura-tion, using a low amount of messages (with a cost that is linear on the number of nodes). These membership services are needed to(More)
This paper introduces a new group communication component designed to provide adaptiveness and high availability in a broad sense. The key element of the system is a switching protocol that enables replacing in runtime the currently used group communication protocol by a different one. Such an architecture can take advantage of the different features of(More)
GlobData is a platform that provides an object-oriented view of wide-area-networked relational databases with replicated data for ensuring high availability. We discuss the embedding of protocols in GlobData, for maintaining the consistency of replications. The protocols are able to alternate between three different modes of consistency. Modes can be(More)
We present a system architecture which facilitates enhanced availability of tightly coupled distributed systems by temporarily relaxing constraint consistency. Three different types of consistency are distinguished in tightly coupled distributed systems - replica consistency, concurrency consistency, and constraint consistency. Constraint consistency(More)
The reliable object invocation mechanism provided by HIDRA for the coordinator-cohort and the passive replica-tion models offers support to ensure that all the replicas of the object being invoked are correctly updated before such an invocation is terminated. This mechanism also ensures that if a primary or coordinator replica crashes, the client is able to(More)
The current standard for fault-tolerance in the Common Object Request Broker Architecture (CORBA) does not support network partitioning. However, distributed systems, and those deployed on wide area networks in particular, are susceptible to network partitions. The contribution of this paper is the description of the design and implementation of a CORBA(More)