# Automatic update of Custom Fields with SNMP/WMI monitors

Custom fields in ManageEngine OpManager allow users to define additional parameters to describe entities monitored in OpManager, providing valuable information about devices in the network infrastructure. From version `128182`, ManageEngine OpManager has the ability to automatically update custom fields using SNMP or WMI monitors. This feature streamlines the process of maintaining accurate inventory notes and databases of network infrastructure by leveraging monitoring data.

## Pre-requisites

- Ensure that the devices are added to OpManager and is monitored via either SNMP or WMI credentials.
- Ensure the Device associated Custom fields are available. [Learn more](https://www.manageengine.com/network-monitoring/help/custom-fields.html)
- Existing default monitors cannot be associated with custom fields.

#### In this help document, you will find the steps to,

- Associate a custom field to a custom performance monitor
  - [From the monitor settings page](https://www.manageengine.com/network-monitoring/help/automatically-updating-custom-fields.html#monitor-settings)
  - [From the device snapshot page](https://www.manageengine.com/network-monitoring/help/automatically-updating-custom-fields.html#device-snapshot)
- [Modify a Custom monitor](https://www.manageengine.com/network-monitoring/help/automatically-updating-custom-fields.html#modify-custom-monitor)
- [View the Custom Monitor and the associated custom fields](https://www.manageengine.com/network-monitoring/help/automatically-updating-custom-fields.html#view-custom-monitors)

## How to associate a custom field to a new custom monitor?

Since existing default monitors cannot have custom fields associated, you'll need to add a new [custom SNMP/WMI monitor](https://www.manageengine.com/network-monitoring/help/add-snmp-monitor.html). A new custom monitor can be added via monitor settings, or from the device snapshot page.

### From the monitor settings page

Follow the below steps to associate a custom field to a custom SNMP/WMI monitor via monitor settings,

1. Navigate to **Settings > Monitoring > Performance Monitor,** and select the **"Add Monitor"** option.

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: Add monitor option under performance monitors](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-0.PNG)

2. Select the device you want to add monitor to, and then choose the required **SNMP OID** from the drop down list, and click on **Query device**.

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: Query device option after choosing required SNMP OID](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-1.PNG)

3. A preview of how your data will be stored in the product will be displayed. Click **Next.**
4. You will be navigated to the Monitor details page.
5. There, enable the **Associate this monitor to a custom field** option.

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: Associate monitor to a custom field option](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-3.PNG)

6. Provide a name to the monitor, and select the required Custom field from the dropdown list, or add a new custom field directly from the drop-down.

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: Monitor name and custom field selection](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-2.png)

7. Enter the time interval. (The minimum should be 3 hours, and the maximum is 24 hours.)
8. Click on **Add monitor** to add the new monitor associated with a custom field.
   - If a monitor is already associated with a device, the custom field will be updated during the next poll.
   - If a monitor is not associated with any devices, the associated custom field will be updated once the monitor is associated with a device and a data poll occurs.
9. The added custom field data can be viewed from the device snapshot page. The data will be updated according to the time interval you have provided.

### From the device snapshot page

Follow the below steps to associate a custom field directly from the device snapshot page,

1. Go to the device's snapshot page via Inventory, to which you want to add a custom field to.
2. Go to the Monitors tab, and select **Add SNMP monitor.**

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: Add SNMP monitor](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-7.png)

3. You will be redirected to the SNMP OID details page.

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: SNMP OID details page](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-1.PNG)

4. Repeat the steps from Step 4.

## Associating/Dissociating custom fields from performance monitor

If a custom monitor has been added previously, it can be edited and a new custom field can be associated to that monitor, or the associated custom field can be removed from it. To edit a custom monitor, follow the below steps,

1. Go to **Settings > Monitoring > Performance Monitor.**
2. Click on the "Edit" icon under the Actions column of the monitor you want to edit.

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: Edit icon adjacent to performance monitors listed](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-9.PNG)

3. Select the required custom field from the drop-down menu, and set the interval, to add or modify the custom field.

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: Interval settings to add or modify custom fields](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-12.png)

4. **To dissociate** the custom field from that monitor, select the custom field as **None**.

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: Custom field none to dissociate the same](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-10.PNG)

5. Click **Next** to update the custom monitor.

## How to view the Custom Monitors associated with Custom Field?

The added custom monitors, and the custom fields can be viewed from the performance settings page. To view the added custom monitors,

1. Go to **Settings > Monitoring > Performance Monitor.**
2. Select Custom field monitor from the **dropdown menu** before the **Add monitor** option. This will list all monitors currently associated with a Device-Associated Custom Field.

![Automatic update of Custom Fields with SNMP/WMI monitors in OpManager: Device-associated custom field list](https://www.manageengine.com/za/network-monitoring/help/images/cust-field-11.PNG)

**Note:**

- At the device template level, monitors with the same custom fields are not allowed.
- Data type compatibility will be checked for custom field associations with monitors:
  - **Custom Field (Text):** Can be associated with a monitor with numeric and string data types.
  - **Custom Field (Numeric):** Can be associated with a monitor with numeric (integer/decimal) values.
  - **Custom Field (Date):** Can be associated with a monitor returning the YYYY-mm-DD format.
- If a monitor is associated with a device, and mapped to a custom field, any manual updates to the custom field from the Device Snapshot Page will dissociate the monitor from the device.
- **Each custom field can only be associated with one monitor for the selected device. Similarly, a custom SNMP monitor can only be linked to one custom field.** If multiple monitors are linked to a custom field, only the first associated monitor will be considered, preventing duplicate data collection.
- Non-inventory details like telephone numbers may need to be updated manually.
- Additionally, the minimum polling interval is 3 hours, while the maximum is 24 hours. If a custom monitor associated with a custom field has a polling interval of less than 3 hours, the monitor data will not update the value.