Data replication is an increasingly important topic as databases are more and more deployed over clusters of workstations. One of the challenges in database replication is to introduce replication without severely affecting perfor- mance. Because of this difficulty, current database products use lazy replication, which is very efficient but can com- promise consistency. As an alternative, eager replication guarantees consistency but most existing protocols have a prohibitive cost. In order to clarify the current state of the art and open up new avenues for research, this paper anal- yses existing eager techniques using three key parameters. In our analysis, we distinguish eight classes of eager repli- cation protocols and, for each category,.
