Rollback segments

	How can I update or delete a big table without blowing rollback
        segments ?
	Imagine you have a HUGE table and need to update it, possibly
	updating the key.  You cannot update it in one go because your
	rollback segments are too small.  You cannot open a cursor and
	commit every n records, because the cursor will close.  You
	cannot have a number of updates of a few records each because
	the keys may change - causing you to visit records more than
	once.