A computer network system for building and/or synchronising a second database based on a first database. Accesses by work units are carried out on the first database from an application workstation, to generate, change or delete contents of the database. A first server and second server interconnected via a data connection guide and maintain the first database and a second database, respectively. The accesses take place using an encapsulation module that receives and decomposes the work units into one or more messages, enters the messages in the first database and sends the messages to the second database. A coexistence controller places change messages sent by the first database in a coexistence database, determines whether all messages of a transaction have been transmitted, determines application program elements for which changes are relevant, if all of the messages of the transaction have been transmitted, and reads out the placed change messages in a correct order.