Re-using an existing db and archiving data

[Mark Hiles]

I've just started using Derby for a uni project and have a couple of 
quick questions.

When creating an embedded database, it seems to get overridden each time 
I run my application. How can I make it create a database the first time 
it runs, and then re-use it in the future?

I'd also like to know if it's possible to select certain data for 
archiving / compression? I've searched for material but can't find anything.

Can anyone point me in the right direction?

Many Thanks..