Change the JDBCNetwork, Station, Site and Channel tables such that they don't contain their codes directly. There's an intermediary table that holds these pieces of information that then joins to the tables to provide the full information. Objects outside the network system wanting to refer to a channel or station instead refer to the id of row in the intermediary table containing the codes they're interested in. This allows the times of the channel and stations and networks to change under their representation without cascading updates.