If all the databases would stay connected, a database operation could be passed on to the other databases. The same modification would be done, and the databases would be synchronized again. Many databases rely on this system. Whenever they get disconnected, they do not allow write access. Most information found in literature describes databases that are connected most of the time.
PIM devices on the other hand are disconnected most of the time. We need to find a way to keep track of the database operations and synchronize them whenever a connection exists.