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Defining and Measuring Conflicts in Optimistic Replication

John Heidemann, Ashvin Goel, and Gerald Popek
University of California, Los Angeles

Abstract

Optimistic replication is often viewed as essential for large scale systems and for supporting mobile computing. In optimistic replication, updates can be made concurrently to different file replicas, resulting in multiple versions of the file. To recover from these conflicting updates, after-the fact conflict resolution actions are required to recombine multiple versions into one. This paper defines these concepts and discusses approaches to measure them in optimistically replicated systems.

Measurement of the number of conflicting updates and conflict resolution is important to judge the practicality of optimistic replication. An environment where conflicting updates are frequent will not be attractive since users cannot assume they have up-to-date data. Although many conflicts can be automatically resolved, some conflicts require user intervention; such conflicts cannot be too common. This paper shows an approach to measure the number of conflicting updates. From this measurement we derive the actual amount of work done by the user or system to resolve conflicts and the minimum amount of work required to resolve conflicts.

Availability

This paper is available in several formats: abstract web page with pointers and cites, gzip'ed postscript, PDF, paper copies can be obtained by mail to the authors. Copyright terms for this paper appear below.

Reference

Heidemann95d: John Heidemann, Ashvin Goel, and Gerald Popek. Defining and Measuring Conflicts in Optimistic Replication. Technical Report UCLA-CSD-950033, University of California, Los Angeles, September, 1995. <http://www.isi.edu/~johnh/PAPERS/Heidemann95d.html>.

@techreport{Heidemann95d,
	author = "John Heidemann and Ashvin Goel and Gerald Popek",
	title = "Defining and Measuring Conflicts
				in Optimistic Replication",
	institution = "University of California, Los Angeles",
	year = "1995",
	number = "UCLA-CSD-950033",
	pages = "11",
	month = "September",
	keywords = "ficus, conflict measurement, conflict definition",
	url = "http://www.isi.edu/~johnh/PAPERS/Heidemann95d.html",
	psurl = "http://www.isi.edu/~johnh/PAPERS/Heidemann95d.ps.gz",
	pdfurl = "http://www.isi.edu/~johnh/PAPERS/Heidemann95d.pdf",
	organization = "University of California, Los Angeles",
}

Copyright

This paper is copyright © 1995 by its authors. Permission to make digital or hard copies of part or all of this work for personal use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that new copies bear this notice and the full citation on the first page. Abstracting with credit is permitted.

To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission of the authors.