Adaptive distributed data management with weak consistent replicated data
Richard Lenz · 1996
The intention of this paper is to suggest a novel concept for distributed data management that allows a flexible adaptation to application needs.The basic idea is to improve data availability and performance of read operations by weak consistent data replication according to the need-to-know principle.Need-to-know means that data only have to be made available where they are needed and only as current and consistent as required by the applications that access these data.This in turn requires to provide means to specify the needs of the applications.ASPECT A(.A_pplication-oriented SPEcification of Consistency Terms) is such a technique that allows to specify weak consistency requirements from an application's point of view.This paper summarizes the motivation and key concepts of ASPECT and details the concept of consistency islands.The consistency island for a certain data item is a set of consistent replicas, which changes its structure over time according to application needs.The consistency island is used to synchronize updates and though it is not bound to a certain copy it behaves like a primary copy, which ensures convergence of replicas.The dynamic and adaptive structure of the consistency island, however enables an increase of performance and higher availability compared to traditional replicaton approaches. I. INTRODUCTIONDistributed Databases traditionally adhere to the principle of ubiquity.According to [25] the main features of this principle are that all data objects are available at any site in the system, "Permission to make digital/hard copy of all or part of this material without fee is granted provided that copies are not made or distributed for profit or commercial advantage, the ACM copyright/server notice, the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery, Inc.(ACM).To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee.