# Transaction Group OPC Data Mode 8.1.12

**URL:** <https://forum.inductiveautomation.com/t/transaction-group-opc-data-mode-8-1-12/56070>\
**Category:** Ignition\
**Created:** [February 12, 2022, 7:05pm UTC](https://forum.inductiveautomation.com/t/transaction-group-opc-data-mode-8-1-12/56070 "2022-02-12T19:05:45Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![bfearnow](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bfearnow/32/3337_2.png) [@bfearnow](https://forum.inductiveautomation.com/u/bfearnow)\
**Post date:** [February 12, 2022, 7:05pm UTC](https://forum.inductiveautomation.com/t/transaction-group-opc-data-mode-8-1-12/56070/1 "2022-02-12T19:05:45Z")

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It was my understanding that if the Group OPC Data Mode is set to “Read” then any OPC items would be refreshed before performing the transaction group operation (i.e. write tag values to a DB). Based on some testing I have done this is not the case. Can someone explain?

Example Setting A:

Trigger Tag (scanned every 1 second)  
Data Tags (set to scan every 5 seconds)  
Transaction Group (evaluating every 2 seconds, I assume this mean it’s only looking for an active trigger every 2 seconds)  
OPC (set to “Read”)  
In this case, the data tags are not refreshed prior to inserting into the DB. Old values are written.

Example Setting B:

Trigger Tag (scanned every 1 second)  
Data Tags (set to scan every 1 second)  
Transaction Group (evaluating every 2 seconds, I assume this mean it’s only looking for an active trigger every 2 seconds)  
OPC (set to “Read”)  
In this case, the correct data tag values are inserted to the DB.

Am I misunderstanding the OPC setting? My goal was to not scan the data tags at a very fast rate until they are actually needed, but it seems like they still need to scan at the same rate or faster than the trigger.

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<div class="post-metadata">

**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:** [February 12, 2022, 7:07pm UTC](https://forum.inductiveautomation.com/t/transaction-group-opc-data-mode-8-1-12/56070/2 "2022-02-12T19:07:41Z")

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It only applies to direct OPC _ **items** _ (dragged from the OPC browser to the transaction group), not to Ignition _ **tags** _ that happen to be type OPC.

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<div class="post-metadata">

**Author:** ![bfearnow](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bfearnow/32/3337_2.png) [@bfearnow](https://forum.inductiveautomation.com/u/bfearnow)\
**Post date:** [February 12, 2022, 7:08pm UTC](https://forum.inductiveautomation.com/t/transaction-group-opc-data-mode-8-1-12/56070/3 "2022-02-12T19:08:14Z")

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Ahhh. That’s helpful. I’ve got some fixing to do. Thanks sir!

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<div class="post-metadata">

**Author:** ![bfearnow](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/bfearnow/32/3337_2.png) [@bfearnow](https://forum.inductiveautomation.com/u/bfearnow)\
**Post date:** [February 17, 2022, 3:05pm UTC](https://forum.inductiveautomation.com/t/transaction-group-opc-data-mode-8-1-12/56070/4 "2022-02-17T15:05:30Z")

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![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/a/f/afe8d3629d047d2847391b017778bc60741fe2a5.png)  
Do these “ReadStructuredTagRequest” events followed by the “readValueIds.size()” indicate that an OPC read is happening? If so, the opc items that are not the trigger are bring read at the same interval as the scheduling rate.

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/1/6/16d932793b86aa04e3c3f570cd8fbb06465e5947.png)

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<div class="post-metadata">

**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:** [February 17, 2022, 6:13pm UTC](https://forum.inductiveautomation.com/t/transaction-group-opc-data-mode-8-1-12/56070/5 "2022-02-17T18:13:26Z")

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They should be reading only when triggered.