SUMMARY: oracle backup recommendations

Sorry for the (extremely) late summary.

I got a few responses.  All approved of the plan, though one person
mentioned that the plan still leaves us exposed during the backup,
when the mirror is broken.  I'm not so sure about that though; I
think that the setup I described originally is effectively a
triple-mirror.  However, there's something I'm not entirely sure
of; can Oracle be backed up in this scenario _without_ putting the
database in backup mode?  I feel like it would definitely be the
safest thing to do, but I also realize it may not be strictly
necessary assuming the mirror does it's job properly.
  
Thanks to:

Vinay Thakral
Stuart Whitby
Tom Davis

Your input is appreciated.

--vince