There are proper ways of doing this: you run the old system in parallel with the new system and you outfit both systems in such a way that all writes are done on both systems. That way the DBs stay in sync.

So you won't have to 'write your code to continue saving some bizarre unnecessary data in the database' and you can have your 'sensible scheme'. It just takes a little bit more care and planning.

> As for the other comment, were they supposed to continue renting out completely unused facilities in case someone came along who thought the old system was better?

They ended up renting a good part of those facilities anyway, the problem was not the money but the fact that certain comms lines had been torn up.

Playing cowboy with critical company data is not a winning strategy.