It is almost impossible to keep things in synch manually. Instead:

  1. Keep each fact in only one central database (not necessarily SQL (Standard Query Language) ) and access it as needed. Since there is only one copy of each fact, there is nothing to get out of synch.
  2. Use some automated tool so that if you change a fact is one place, it automatically updates the others.
  3. Write a sanity checker you run periodically to ensure all is consistent. This is the strategy compilers use.
  4. Document the procedures needed to keep all in synch if you change something and rigidly and mechanically follow them.
~ Roedy (1948-02-04 age:70)