# UDT with tag value being paramater clears **URL:** \ **Category:** Ignition\ **Tags:** perspective, ignition81\ **Created:** [August 7, 2025, 4:23pm UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491 "2025-08-07T16:23:55Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![scadafan](https://avatars.discourse-cdn.com/v4/letter/s/90db22/32.png) [@scadafan](https://forum.inductiveautomation.com/u/scadafan)\ **Post date:** [August 7, 2025, 4:23pm UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491/1 "2025-08-07T16:23:55Z")
In Ignition I have a UDT in it there is a tag that references a value in a parameter it works fine but after a couple of weeks it just goes blank and clears the value in the tag even though it is still present in the udt parameter any idea why? ---
**Author:** ![amarks](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/amarks/32/45610_2.png) [@amarks](https://forum.inductiveautomation.com/u/amarks)\ **Post date:** [August 7, 2025, 8:53pm UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491/2 "2025-08-07T20:53:26Z")
Need more information. What type of tag is it? How does the tag use the parameter? ---
**Author:** ![scadafan](https://avatars.discourse-cdn.com/v4/letter/s/90db22/32.png) [@scadafan](https://forum.inductiveautomation.com/u/scadafan)\ **Post date:** [August 7, 2025, 9:56pm UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491/3 "2025-08-07T21:56:27Z")
Its a string tag it is writing to and the its a straight read. The parameter is the name of a machine lets say Machine 1 and then a string tag within the UDT pulls that machine name and puts it in a string. Hopefully that makes more sense ---
**Author:** ![amarks](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/amarks/32/45610_2.png) [@amarks](https://forum.inductiveautomation.com/u/amarks)\ **Post date:** [August 7, 2025, 10:04pm UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491/4 "2025-08-07T22:04:32Z")
Something must be writing to it. Make a tag change script and log the change. ---
**Author:** ![scadafan](https://avatars.discourse-cdn.com/v4/letter/s/90db22/32.png) [@scadafan](https://forum.inductiveautomation.com/u/scadafan)\ **Post date:** [August 7, 2025, 10:16pm UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491/5 "2025-08-07T22:16:57Z")
The thing is the paramater doesnt change and neither does the tag value but historian shows that tag as blank. So nothing is actually changing on the tag itself but just wont record and then the only way I can fix it is by writing something else in there and then writing back the value it had originally ---
**Author:** ![robertm](https://avatars.discourse-cdn.com/v4/letter/r/ea5d25/32.png) [@robertm](https://forum.inductiveautomation.com/u/robertm)\ **Post date:** [August 7, 2025, 10:23pm UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491/6 "2025-08-07T22:23:59Z")
Confused…post 1 you said the tag value changed. Now you’re saying it doesn’t. If it’s changing in historian, how do you have the historical collection set on the tag? How are you determining the value isn’t there in historian? ---
**Author:** ![Chris\_Bingham](https://avatars.discourse-cdn.com/v4/letter/c/e5b9ba/32.png) [@Chris\_Bingham](https://forum.inductiveautomation.com/u/Chris_Bingham)\ **Post date:** [August 7, 2025, 10:46pm UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491/7 "2025-08-07T22:46:46Z")
Speculation - you might be querying for data that just doesn’t exist within the window of time that you’re querying against. If the tag hasn’t changed in value in the last month, and there is no periodic force-insert configured, there will be no results returned in a query for data over the last couple of weeks. If this is the case, either change the query to always return the last known value in the historian -or- set your tag history settings to force an update periodically (weekly?). ---
**Author:** ![scadafan](https://avatars.discourse-cdn.com/v4/letter/s/90db22/32.png) [@scadafan](https://forum.inductiveautomation.com/u/scadafan)\ **Post date:** [August 8, 2025, 2:07am UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491/8 "2025-08-08T02:07:19Z")
This is what I thought but I am writing this to a csv file and i am pulling all data even if it doesnt change and it works fine for months and then randomly one day it stops. The machine name never changes by the way ---
**Author:** ![amarks](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/amarks/32/45610_2.png) [@amarks](https://forum.inductiveautomation.com/u/amarks)\ **Post date:** [August 8, 2025, 1:06pm UTC](https://forum.inductiveautomation.com/t/udt-with-tag-value-being-paramater-clears/109491/9 "2025-08-08T13:06:08Z")
My guess would be that the value has never changed so historian doesn’t log it, assuming that the historian is set up to log the tag on-change. Why are you logging a static tag?