Abstract: A data management system for sharing data between remote sites of a data network A data storage medium is located at each site, operative to store first and second data collections. The data management system includes a primary data replication module, a replication control mechanism and a secondary data replication module. The primary data replication module replicates data from at least a portion of the first data collection of each data storage medium to the same first portion of the first data collection of predetermined ones of the other data storage media. The replication control mechanism includes a data structure that is stored in the first data collection of each data storage medium, whereby data from the data structure is replicated by the primary data replication module from each data storage media to the respective predetermined other data storage media. This data structure contains data representative of modifications made to the second data collection of each data storage medium.