Deening and Measuring Connicts in Optimistic Replication

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 diierent le replicas, resulting in multiple versions of the le. To recover from these connicting updates, after-the fact connict resolution actions are required to recombine multiple versions into one. This paper deenes these concepts and discusses approaches to measure them in optimistically replicated systems. Measurement of the number of connicting updates and connict resolution is important to judge the prac-ticality of optimistic replication. An environment where connicting updates are frequent will not be attractive since users cannot assume they have up-to-date data. Although many connicts can be automatically resolved, some connicts require user intervention; such connicts cannot be too common. This paper shows an approach to measure the number of connicting updates. From this measurement we derive the actual amount of work done by the user or system to resolve connicts and the minimum amount of work required to resolve connicts.