US Patent 6839752 Group data sharing during membership change in clustered computer system

An apparatus, program product and method utilize subgroup-specific leader members to exchange group data between group members during the handling of a request to organize members into a group in a clustered computer system, e.g., when handling a membership change operation such as a merge or join. Such subgroup leaders may be determined locally within individual subgroup members, and moreover, the subgroup members may locally track the transmission status of group data for the various subgroups. Each subgroup includes one or more members that are known to store group data that is coherent among all subgroup members.