# UDT Parameters in OPC tags

**URL:** <https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228>\
**Category:** Ignition\
**Created:** [January 31, 2023, 6:10pm UTC](https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228 "2023-01-31T18:10:32Z")\
**Posts on this page:** 8\
**Page:** 1

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**Author:** ![nicholas.gutt](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nicholas.gutt/32/25670_2.png) [@nicholas.gutt](https://forum.inductiveautomation.com/u/nicholas.gutt)\
**Post date:** [January 31, 2023, 6:10pm UTC](https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228/1 "2023-01-31T18:10:32Z")

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Ignition Version 8.1.17

Can someone tell me how using UDT parameters in fields OPC Server and OPC item path will affect tag performance?

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**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [January 31, 2023, 6:18pm UTC](https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228/2 "2023-01-31T18:18:22Z")

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I don't think you can use it for OPC Server.

It shouldn't have any affect though. They aren't expression bindings, they are evaluated once when the tag is initialized, not continuously in reaction to some change.

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**Author:** ![nminchin](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/nminchin/32/6911_2.png) [@nminchin](https://forum.inductiveautomation.com/u/nminchin)\
**Post date:** [January 31, 2023, 8:04pm UTC](https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228/3 "2023-01-31T20:04:46Z")

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UDTs would be utterly useless if you couldn't use them inside of the opcitempath - that's literally the place they're used most often

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**Author:** ![witman](https://avatars.discourse-cdn.com/v4/letter/w/d2c977/32.png) [@witman](https://forum.inductiveautomation.com/u/witman)\
**Post date:** [February 1, 2023, 4:25am UTC](https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228/4 "2023-02-01T04:25:55Z")

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Yes, use the parameters to make UDTs really useful. And you can use them for server--we set it as a parameter on all of our UDTs and use it on all the OPC tag members within them:  
 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/1/f/1f3d12e223a78568dff2c7bf6b606eeb34acfff6.png)

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<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [February 1, 2023, 2:19pm UTC](https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228/5 "2023-02-01T14:19:51Z")

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Nice, my memory is unreliable. Maybe at some point in the past it wasn't possible?

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**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 1, 2023, 2:27pm UTC](https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228/6 "2023-02-01T14:27:01Z")

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How long have UDTs been part of the platform?

/me runs away...

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<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [February 1, 2023, 2:30pm UTC](https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228/7 "2023-02-01T14:30:38Z")

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Wasn't the server only a dropdown and not bindable before 8.x?

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**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 1, 2023, 2:52pm UTC](https://forum.inductiveautomation.com/t/udt-parameters-in-opc-tags/69228/8 "2023-02-01T14:52:37Z")

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It was a dropdown, but you could also type what you wanted in it. (I just opened a VM to check.)