Just a thought, from RESULTS ORIENTED
Business is booming. Your stores are growing. A greater variety of products are being sold. You find that you are running out of product numbers. So your seven digit product number needs to increase to eleven.
Luckily this only affects one database. But how many applications? You think you know, but can you be sure? Refactoring is a way of keeping the 7-digit and introducing the 11-digit product number at the same time.
Now you can change your inventory and vendor ordering systems so that you can get those new products in. However, you can leave the rest of the applications alone. Once that work is complete, you can tackle, say, your Point-of-Sale (POS) systems. The refactoring process can also identify which system is using the 7 or 11 digit number. So a few "unknown" systems will come to light, and you upgrade those.
Now the 7-digit product number can be removed.

A very pragmatic approach to a tough problem. This can keep the business growing, without huge bills, and massive teams working on all systems at once. But there is a cost. There will be an extra load on the database so you need to be firm with the end-date. You cannot keep the two product numbers out there forever. Because, next month the product description is too short, then the vendor name, then.......and before you know it, you have 'barnacles' all over the database.

Source: Presentation by Scott Ambler at the Toronto CIPS meeting 2006Feb09