Cluster based replication solutions are an attractive mechanism to provide both high-availability and scalability for the database backend within the multi-tier information systems of service-oriented businesses. An important issue that has not yet received sufficient attention is how database replicas that have failed can be reintegrated into the system or how completely new replicas can be added in order to increase the capacity of the system. Ideally, recovery takes place online, i.e, while transaction processing continues at the replicas that are already running. In this paper we present a complete online recovery solution for database clusters. One important issue is to find an efficient way to transfer the data the joining replica needs. In this paper, we present two data transfer strategies. The first transfers the latest copy of each data item, the second transfers the updates a rejoining replica has missed during its downtime. A second challenge is to coordinate this transfer...