Methods and systems for data maintenance in an offline-distributed database network system, which comprises a central system having a central database, and node systems having local databases capable of containing different subsets of data from the central database. First, change information relating to data stored in at least one of the central and local databases is recorded in at least one of the node systems. Then, a replication object including the change information is transmitted, if an online connection is available, from the recording node systems to the central system or from the central system to the recording node systems. The recipients of the replication object are determined based on at least one lookup table in the central system. The lookup table is updated in accordance with the change information of the replication object.