Background: PI Server 2012, OPC Interfaces installed on 5 nodes communicating with primarily Rockwell ControlLogix PLC's (a couple of Modbus ones in the mix is all). Using Matrikon OPC Server for AB for the Rockwell stuff and Matrikon OPC server for Modbus for the others. Currently about 1200 tags, but plan to expand the system to say upward of 5000 in the next 2 years.
Most of the tags that we setup to start with are Polled...with the majority of them set to 10 second scan class. I was nervous at the beginning that we didn't want to create to much traffic, events, etc. but have since realized that this is really not much of an issue on the PI server and doesn't seem to be an issue for the interface nodes either at this point.
Now that I know more about PI and how it works, it seems to me that Advise tags are really the way to go. I have a couple of questions related to this:
1. Can folks give me any feedback on why Advise is better than Polled (or vice versa) or really what the benefit of each might be in certain situations.
2. The majority of my PLC's are not doing anything over the network...other than talking with PI through the Matrikon OPC server (some are however)...but should I be concerned about loading on the PLC's if I were to simply set up most all the tags as Advise with 1 second scan class?
3. Anything I should consider or watch out for when I go back and change the scan classes on the current tags from Polled (10 second) to Advise (1 second)? I understand the "don't mix polled and advise tags in the same scan class and scan class 1 is reserved for advise tags).
Kind of looking for general expert guidance on this topic...how it works, benefits and drawbacks, etc. Any links to great articles or how to's would be appreciated too.
Thanks!