backing up a db, jdbc, SQL syntax, etc...

Hello together!

I come up with a conglomerat of questions ;-)

o What do you think is the best way to backup the data stored in a  postgres db? Backing up the whole db-file, doing a
dumpinto ascii files with seperators or whater ever method else?
 


o Is there a maximum number of connections to the backend that could  run us into trouble if lot's of users who are
connectedvia jdbc do not close their applets? 
 

o Do I have to take any speacial locking mechanism in SQL into account  for a high number (~500) of users. I only use
SELECTs,UPDATEs, INSERTs and  NEXTVALUE from a sequence over jdbc. Problems with caches, memory/connection  ...?
 

o Does anyone know how I can throw out (stop) a java applet completly out of the  java interpreter in a browser; so
thatall resources and memory are released. In the moment this only happens when I kill the browser (netscape on linux)
 
 Here some Q's which I posted some times ago in the novice-list but where  not answered and so are still open (for me,
naturally:-) )
 

o Where is the difference between:
       SELECT f.title, f.did, d.name FROM dist d, films f WHERE f.did=d.did; and       SELECT films.title, films.did,
dist.nameFROM dist JOIN films       USING(did);
 
 or a formulation with inner join? Don't the result in the same output? 
 If I'm not mistaken, why do I get a inner join not yet implemented information, would a inner join have to be
implementedin a different  way in the db-backend?
 




Greetings from Austria, 
       Georg Ritter


-- 
--------------------------------------------------------------------- student at department of physics University of
Innsbruck,Austria            Georg.Ritter@uibk.ac.at