# Log Errors: No Scan Class Information Found for Tags

**URL:** <https://forum.inductiveautomation.com/t/log-errors-no-scan-class-information-found-for-tags/25786>\
**Category:** Ignition\
**Created:** [June 12, 2019, 9:41pm UTC](https://forum.inductiveautomation.com/t/log-errors-no-scan-class-information-found-for-tags/25786 "2019-06-12T21:41:19Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Dryhops](https://avatars.discourse-cdn.com/v4/letter/d/8797f3/32.png) [@Dryhops](https://forum.inductiveautomation.com/u/Dryhops)\
**Post date:** [June 12, 2019, 9:41pm UTC](https://forum.inductiveautomation.com/t/log-errors-no-scan-class-information-found-for-tags/25786/1 "2019-06-12T21:41:19Z")

</div>

I just upgraded to 7.9.11 LTS and noticed intermittent errors in the log:

No scan class information found for tags. All returned data will be bad quality.

I turned Tags.History.Query.DataLoader.DB to DEBUG:

 ![Capture](https://us1.discourse-cdn.com/inductiveautomation/original/2X/e/e9f45853a726e2b3837c7b97eb79e4d7829739c6.png)

The offending tag does not exist:  
 ![Capture2](https://us1.discourse-cdn.com/inductiveautomation/original/2X/4/4719339cadf804e096f4a5ec6e6bb1f6ad98bcfb.png)

Is there a way I can rebuild the historian tag list, or otherwise somehow determine which tags in the historian are no longer valid? I have many thousands of tags, so individually checking them would be a challenge.