Found my own answer, you can disable session persistence in sun-web.xml:
http://blogs.sun.com/jluehe/entry/how_to_disable_persisting_of
Just had to refine my googling a bit :-)
Gabor Szokoli
On Sun, Mar 23, 2008 at 9:55 AM, Gabor Szokoli <szocske_at_gmail.com> wrote:
> I shut down and restart glassfish with asadmin stop-domain then start-domain.
> Not a single java process runs on the server in between, confirmed by ps.
> But when I access the servlet from a browser again, the session seems
> to still exist!