Issues when updating running apps?

Hello all,

I have a very basic question I hope someone can help me with.

I'm not sure on how to package an application so that updating it while=20
it's running won't cause any problems. For instance, I'm packaging a=20
quite typical java app that has a swing GUI and stores its data in a=20
database. In the event of an update requiring modifications to the=20
database schema I had thought of including these in the %pre or %post=20
sections, but I assume this could lead to the app breaking to pieces if=20
the old version is running when the changes meant for the newer version=20
are made. A similar problem could occur if I update some jar and the=20
running app happens to load some classes from it that won't work=20
properly with the older version. Am I making any sense with this?

How can I get around these issues? are there other I should look out for=20
that I'm not considering?

I'd highly appreciate any advice/tips/links you could give me.

Regards.

Adri=E1n.