It seems to be more of a case of avoiding 'planned downtime' in order to increase 'availability' while at the same time increasing the possibility and length of 'unplanned downtime'.
Check out the following:
http://en.wikipedia.org/wiki/High_availability
Lots of good links in the wiki ...
RegardsRudy KomacsarSenior Database Administrator"Ave Caesar! - Morituri te salutamus."