Efficient method for fetching subset of large array from OPC UA

Ignition
1

For reasons outside of my control, I need to create a custom alarm banner and alarm history. I'm using OPC UA and a Beckhoff PLC. I'm stuck on the alarm history. The PLC currently keeps track of the last 1000 alarms and I was hoping to pull 50-100 elements at a time and display them in a table. I could add buttons to shift the array subset to fetch the next 50-100 elements. The PLC alarm array could easily grow to 2000 or 3000 if deemed necessary so I only want to pull a piece of it. Does anyone have a good method for pulling a subset of an array without fetching the whole array from the PLC? I was hoping to use like 50 memory tags that were indexes into the array. I could feed these into dynamic array element tags but that doesn't seem possible. Anyone have some suggestions or things to try?

2

OPC Item Paths are bindable, so it won't be truly dynamic like you're hoping, but two ideas:

  1. use system.tag.configure to edit the OPC Item Paths as needed
  2. create 50 memory tags, but use a timer script or something to read the elements and write them to those tags. the script can be as dynamic as you want
3

Maybe a UDT with 50 memory tags and a parameter for offset?

bind would be something like:
{offset}
{offset +1}
{offset +2}
{offset +3}
etc...

then you would set offset to 0 for the first 50 and set offset for that specific udt instance each change. I believe you can edit params for UDTs programmatically.