Expert (880 points)
After looking for a good description of Active Memory and posting a question with no responses, I decided to just put it to the test. I wrote a small C++ app that would either write to or read from 500 MB of RAM. Here is what I learned.
My first run through the program wrote a random character to every index in the 500 MB array.
Next it wrote to random indexes.
Next it read from random indexes.
In between all runs, the program was stopped and memory reclaimed by ESX.
It was about five minutes before the active memory counter in the VIC started to taper off.
So the easy description, "Active memory is memory that is either written to or read from within the last five minutes".
Charles Killmer