OK thanks. That helps me clarify my question - as "what triggers shares" is really the specific question, as opposed to limits or reservations. In this case I am concerned only about shares, rather than limits and reservations. With limits and reservations, it is very clear. With shares, I haven't found the answer yet. I have started googling his articles, but have not yet found the info as per my post above - i.e. what is the exact metric and data counter value upon which shares take affect for CPU and RAM.
I changed the title of my post to "What Triggers Shares" to clarify.