# Bad\_ReadOnly when updating a UDT tag Value

**URL:** <https://forum.inductiveautomation.com/t/bad-readonly-when-updating-a-udt-tag-value/40767>\
**Category:** Ignition\
**Created:** [November 18, 2020, 4:32pm UTC](https://forum.inductiveautomation.com/t/bad-readonly-when-updating-a-udt-tag-value/40767 "2020-11-18T16:32:41Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![aamrc](https://avatars.discourse-cdn.com/v4/letter/a/dfb087/32.png) [@aamrc](https://forum.inductiveautomation.com/u/aamrc)\
**Post date:** [November 18, 2020, 4:32pm UTC](https://forum.inductiveautomation.com/t/bad-readonly-when-updating-a-udt-tag-value/40767/1 "2020-11-18T16:32:41Z")

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Hi,

When I try to edit some tag values that sit under a UDT within Designer I get an error `Bad_ReadOnly` popup. I’m puzzled what I’m doing wrong as some tags that sit under the same `Edge Nodes` but are not under a UDT can be edited (i.e. I can see Ignition issuing a `DCMD` message over MQTT).

I’m using Ignition + MQTT Engine. I create tags with the Node-RED Sparkplug client.

What can cause this error?  
I’m running Ignition 8.1.

Art

![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/c/f/cfd1858e8d3c1579c25695fa66e76542d864079b.png)

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<div class="post-metadata">

**Author:** ![aamrc](https://avatars.discourse-cdn.com/v4/letter/a/dfb087/32.png) [@aamrc](https://forum.inductiveautomation.com/u/aamrc)\
**Post date:** [November 19, 2020, 11:48am UTC](https://forum.inductiveautomation.com/t/bad-readonly-when-updating-a-udt-tag-value/40767/2 "2020-11-19T11:48:05Z")

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To add to this I’m able to `system.tag.copy` and the Read Only field is set to `false` by default.

I’ve tried 2 commands:  
`system.tag.writeBlocking([cmd_resp_path], ["Command Rejected. Permission Error"], 5000)`  
`system.tag.write(cmd_name_path, "Command Rejected. Original Command")`

The Legacy `system.tag.write` is the only one that gives an error:

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/e/f/ef8c6e07466d0a1f6c3e8b76866a8cc2d06d872c.png)

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/b/2/b2c136ec681bd7dca13e2457677af99adf4247a0.png)