best practice for handling database schema changes

[Tobias SCHOESSLER]

hi,
What is the best practice for handling changes to the database schema once a cayenne mapping was created?
We use the 'reverse engineer from database' feature to create an initial mapping. But then we usually have to do manual changes like map some pks, add flattened relationships, etc.
If then the database schema needs to be changed we usually have a problem as 'reverse engineer from database' overwrites everything. There seems to be the possibility to replace only selected tables but if you do this the relationships are messed up. Is there a way to  merge the changes with the current model/mapping?

thanks

Tobias