Disconnected data

Question

Hi, I'm doing my first really disconnected data application. And my problem is about handling primary (and foreign) keys. I have an application that handles customers and their orders. I need to be able to add (disconnected) new customers and new orders to them. So, I'll have to find a way, to give a new primary key to customers so I can use it when making new orders for them. That's not a problem (is it?), but how about persisting data to a db, when the app gets in connected environment? Somehow, I should give REAL primary keys, and change the corresponding keys in orders table. How to do that? Thanks!