You might get away with no GC before a snapshot but please remember  
that you do need to do various shutdown work to make the written  
snapshot have a serious chance of being restartable.

I'm not in a position to provide a list; never tried it so I don't  
know what would go wrong. I _do_ know that a similar 'neat trick'  
cost PPS a very large amount of engineer time (and therefore direct  
money out of my budget as manager of the dept. back then) when so  
twerp at a Large Oval Logo Company decided that snapshotting in the  
background every few minutes would be a Good Idea. I can't recall the  
details any longer - getting too old - but it took _months_ to track  
down the problem. It was escalated to a total emergency, the GC was  
blamed, my engineers were blamed, I was blamed, the customer was  
adamant that they had never, would never, could never have done  
anything that could have caused it. When we solved the problem and  
proved it was their code I don't recall anybody even saying thanks.

So all in all I'm not sure I'd recommend doing a regular raw snapshot  
in the background.

tim
-- 
tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim