I have a Pix501 running 6.3(5) software and PDM 3.0(4). I am using the graphing function of the PDM interface to graph interface bit rates. When I select a new history range, it seems that the data collection only begins when I select that range. I can't see any history unless I keep the graph window open. I could swear that it was stored last time I used this function so that you could log into PDM and see the last 12 hours for example. Maybe I am wrong. Is this not the case? Is there a function to enable the data to be collected while not actively graphing?