Ed,

>I see you already received all answers, i.e. basically you can have as many datasessions as you want but you better control each switch explicitly in code, i.e. using SET DATASESSION TO every time you really want to do it.

I don't agree that you need to issue SET DATASESSION TO whatever number explicitly in every case.

For example, if you wrap up some old code inside methods of a class based on Session, you instantiate the class and call the methods without worrying about changing the datasession explicitly. As long as your class is well-encapsulated and doesn't depend on any state of databases or tables outside of itself, you don't need to explicitly set anything.