# OPC Array Write: The access level does not allow writing to the Node

**URL:** <https://forum.inductiveautomation.com/t/opc-array-write-the-access-level-does-not-allow-writing-to-the-node/84227>\
**Category:** Ignition\
**Tags:** python\
**Created:** [January 12, 2024, 8:01pm UTC](https://forum.inductiveautomation.com/t/opc-array-write-the-access-level-does-not-allow-writing-to-the-node/84227 "2024-01-12T20:01:02Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![ajrowe](https://avatars.discourse-cdn.com/v4/letter/a/8c91f0/32.png) [@ajrowe](https://forum.inductiveautomation.com/u/ajrowe)\
**Post date:** [January 12, 2024, 8:01pm UTC](https://forum.inductiveautomation.com/t/opc-array-write-the-access-level-does-not-allow-writing-to-the-node/84227/1 "2024-01-12T20:01:02Z")

</div>

We have a python program that writes to an A-B ControlLogix PLC via an Ignition Allen-Bradley Logix Driver OPCUA device connection. If try to write a 20-REAL array at once, we get the error: "The access level does not allow writing to the Node." If we cycle through each element of the array and write them individually the write succeeds. Writing individually ends up being a lot slower.

Is there an OPC Server setting change that would allow the single write, or any other ideas?

---

<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:** [January 12, 2024, 8:52pm UTC](https://forum.inductiveautomation.com/t/opc-array-write-the-access-level-does-not-allow-writing-to-the-node/84227/2 "2024-01-12T20:52:52Z")

</div>

Not a setting, but a driver change would do. My alternate EtherNet/IP driver for Ignition supports array reads and writes.

---

<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:** [January 13, 2024, 12:49am UTC](https://forum.inductiveautomation.com/t/opc-array-write-the-access-level-does-not-allow-writing-to-the-node/84227/3 "2024-01-13T00:49:53Z")

</div>

> [@ajrowe](#):
>
> If try to write a 20-REAL array at once, we get the error: "The access level does not allow writing to the Node."

The driver doesn't expose arrays, just folders with an element per array. Is this what you mean?

---

<div class="post-metadata">

**Author:** ![ajrowe](https://avatars.discourse-cdn.com/v4/letter/a/8c91f0/32.png) [@ajrowe](https://forum.inductiveautomation.com/u/ajrowe)\
**Post date:** [January 13, 2024, 9:00pm UTC](https://forum.inductiveautomation.com/t/opc-array-write-the-access-level-does-not-allow-writing-to-the-node/84227/4 "2024-01-13T21:00:58Z")

</div>

I'm not sure I understand "just folders with an element per array." Can you point me to some documentation?

Thanks

---

<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:** [January 13, 2024, 9:06pm UTC](https://forum.inductiveautomation.com/t/opc-array-write-the-access-level-does-not-allow-writing-to-the-node/84227/5 "2024-01-13T21:06:55Z")

</div>

> [@ajrowe](#):
>
> not sure

IA's Logix driver doesn't support specifying a OPC Item Path of an entire array, to get an array in a single tag. Each element of an array must be addressed with a separate OPC Item Path in a separate Ignition tag. (But bulk operations writing multiple consecutive elements will be optimized at the protocol level.)

My alternate driver **does** allow complete 1-D arrays of numeric types to be treated as a single tag, both for read and write. Though only complete writes of that array are supported through the tag.

Consider having your python driver write the 20 elements in a **single batch**. I suspect you will find that suitably performant.

---

<div class="post-metadata">

**Author:** ![ajrowe](https://avatars.discourse-cdn.com/v4/letter/a/8c91f0/32.png) [@ajrowe](https://forum.inductiveautomation.com/u/ajrowe)\
**Post date:** [January 16, 2024, 3:11pm UTC](https://forum.inductiveautomation.com/t/opc-array-write-the-access-level-does-not-allow-writing-to-the-node/84227/6 "2024-01-16T15:11:33Z")

</div>

OK, thanks for your help.