It probably happened to you as well... You develop a product, and after you successfully install it at your customers sites, you end up with dozens of versions/revisions of your product. Each revision has its specific SW, with appropriate DB schema, filled with your product initial data (here again, different for each revision) and customer data. How do you manage this DB changes ? What happen when you have dozens of customers with dozens of deployment revisions ? How to support more than one DB ?

These are some of the questions I had to answer on one of Tikal existing customers projects I'm involved with. The questions above are just example for the issues you have to deal when it comes to DB change management.