---
title: Add a Node
slug: litmusedge/uo5LbsQR8g__dzcwV4uKh
description: You can manually add nodes to the OPC UA hierarchy. 
docTags: 
createdAt: 2022-09-26T14:14:20.000Z
---

The OPC UA hierarchy is the address space Litmus Edge (LE) exposes to OPC UA clients. Each node you add becomes part of that address space. Folder and device nodes define the structure. Tag nodes subscribe to a topic and expose its value. Folder and device nodes are structural. Only a tag node returns a value to a client.

Adding a node takes effect immediately. You do not need to restart the OPC UA server and connected OPC UA clients retain their existing sessions and subscriptions. Changes to security policy, network and endpoint settings, or other server configuration parameters do require a restart. See [Manage the OPC UA Server](docId\:jwy5c4KOBCPA8vwezRGcn) to learn more. 

LE adds a new node under whichever node is selected in the Hierarchy pane, or at the root when nothing is selected.

# Node types

| Type   | Represents                                                                | Subscribes to a topic |
| ------ | ------------------------------------------------------------------------- | --------------------- |
| Folder | An edge device or a site, such as an industrial plant                     | No                    |
| Device | A device on the plant floor, such as a boiler or a lathe PLC              | No                    |
| Tag    | A specific register on a device, such as a temperature or pressure sensor | Yes                   |

# How a tag receives data

A tag node subscribes to the topic you give it. The value it returns to OPC UA clients is whatever that topic last published.

The topic does not have to come from a DeviceHub device. Any topic on the message broker works, including topics published by flows, connectors, and Digital Twins instances.

The payload must be a JSON object containing at least `value` and `success`.

```json
{
  "value": 11.11,
  "success": true
}
```

If the payload also includes a `statusCode` field, the OPC UA server uses that value for the node's status instead of `success`. Otherwise, the OPC UA server continues to use success. DeviceHub tags publish `statusCode` when **Publish Additional Attributes** is enabled on a device . Currently supported on Gen2 C++ drivers only. See [Connect a Device](docId\:pF5pwEP7Ata1NC7c0yQu_) to learn more.

# Add a node

**To add a node:**

1. Navigate to **OPC **>** Hierarchy**.
2. In the *Hierarchy* pane, select the parent node for the new node. To add the node at the root, select nothing.
3. Click the **Add **icon.

   ![](https://api.archbee.com/api/optimize/SSUUxKZUk9bFTEPNn_6Zo/0mrqKqiujnEL9gqaPy8Db_image.png)
4. Select **Folder**, **Device**, or **Tag**.
5. Enter the node details. A folder or device node needs a name only. For a tag node, see the field table below.
6. Click **Add**.
7. Click the **Save **icon.

## Tag node fields

| **Field**   | **Description**                                                                                                                        |
| ----------- | -------------------------------------------------------------------------------------------------------------------------------------- |
| Node name   | A descriptive name. This is what an OPC UA client sees when it browses the hierarchy.                                                  |
| Topic       | The topic that feeds this node.                                                                                                        |
| Data Type   | The OPC UA data type the node presents to clients. See [Data Type Mapping](docId\:m4GyfS_wBkv-O8I6zZnJi).                              |
| Access Type | The access clients have on the node. **R** allows clients to read the value, **W** allows them to write to it, and **RW** allows both. |

# Considerations

- **Removing a node removes everything under it.** Deleting a folder or device node also deletes its child nodes and their configurations.

# Related topics

- [Data Type Mapping](docId\:m4GyfS_wBkv-O8I6zZnJi) 
- [Import Nodes](docId:65tWv020IysiiI7ynckHs) 
- [Manage Nodes](docId\:I4ITuzNDt1LggCL6uzGKk) 
- [Manage the OPC UA Server](docId\:jwy5c4KOBCPA8vwezRGcn)