# Opc read values efficiency gains or better approaches **URL:** \ **Category:** Ignition\ **Tags:** scripting\ **Created:** [July 3, 2025, 1:39am UTC](https://forum.inductiveautomation.com/t/opc-read-values-efficiency-gains-or-better-approaches/108081 "2025-07-03T01:39:26Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [July 3, 2025, 1:53am UTC](https://forum.inductiveautomation.com/t/opc-read-values-efficiency-gains-or-better-approaches/108081/2 "2025-07-03T01:53:32Z")
That is a tag's `valueChange` event, which is not a safe place to use any `system.opc.*` functions--you risk locking up all tag event processing. Similarly, it isn't safe to do DB operations either, except for fire-and-forget inserts through the Store and Forward system. Finally, it is usually racy to use a single handshake tag--use two, one only written by the PLC, and an echo that is only written by Ignition. The correct place for such busy and dangerous code is a project library script function called from a tag change event in a project's gateway events. (Not on the tag.) Finally, you need to investigate how well your device is actually performing, comms-wise. While AB Logix PLCs tend to support way more comms than other brands, in my experience, it is rather easy to screw that up with poor architecture (in the PLC) and with certain kinds of newbie mistakes (drag-n-drop of all the PLC tags from OPC browser to Ignition Tag Browser being #1). Do you even know if your PLC comms are overloaded? (Device diagnostics.) Some reading (follow links, too): > [@Ignition & Logix Best Practice Tips for better communications](https://forum.inductiveautomation.com/t/ignition-logix-best-practice-tips-for-better-communications/60386): > > Hi All, After a whole bunch of issues I have gone down the rabbit hole of what is wrong with our setup on site. I will preface this by saying I a relatively new to all of this.... so be gentle stuck_out_tongue Based on much reading(such wow) I believe I have a list of things our site could take away for a better system. Some of them are easy to implement, whilst some of them need... significant work to realize. Especially the AOI approach in point 5 expressionless Before going too far a… --- _[View the full topic](https://forum.inductiveautomation.com/t/opc-read-values-efficiency-gains-or-better-approaches/108081)._