I'm about to write a database app using Java/JDBC The DB requirements
are pretty straight: transactions, foreign keys, RI, soft DBK
generation, cursors but no need for stored procedures or triggers.

The app will consist of a scheduled update that runs every day for
minutes rather than hours and an ad-hoc query that will be used rather
less often with little or no overlap with the update task.  IOW, the
database will be idle much longer than  it will be busy.

I'm intending to use either Postgresql or Derby and I'm interested in
the resource consumption of these two when they are idle:
- Postgresql runs as a permanent daemon, so does it absorb RAM or cycles
  when its idle or does it swap out entirely?
- Derby can run as a permanent daemon but it can also be used as part of
  the app, which would not use any resource when idle but startup and
  shutdown time becomes an issue

Any feedback of experience round this area would be helpful.

BTW, this is posted to both c.l.j.p and u.c.o.l because both NGs have
knowledgeable members on this topic but, I suspect, little overlap
amongst their regulars.