> For the complete documentation index, see [llms.txt](https://docs.decube.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.decube.io/data-quality/how-to-set-up-monitors/set-up-volume-monitors.md).

# Set Up Volume Monitors

A Volume monitor tracks how many rows are added to a table in each scan window and alerts you when that increment falls outside the expected range. It is the right tool when you care about *how much* data arrived — not just whether it arrived.

## Freshness vs Volume: which to use

| Goal                                              | Use           |
| ------------------------------------------------- | ------------- |
| Detect that data **arrived** (or didn't)          | **Freshness** |
| Detect that the **right amount** of data arrived  | **Volume**    |
| Table receives data on a known schedule           | **Freshness** |
| Table grows by a predictable row count per period | **Volume**    |

If you need both signals, create one monitor of each type on the same table.

## How the Volume monitor works

The Volume monitor measures the **increment** — the number of new rows added since the previous scan — not the total row count of the table. The ML model trains on historical increments to establish a normal range, and raises an incident when a new increment falls outside it.

{% hint style="warning" %}
**Volume and row deletions**: if rows are deleted from a table and you use **All Records** mode, the measured increment can be negative or artificially small. This produces incorrect deltas. Use **Timestamp** row creation on tables where rows may be deleted.
{% endhint %}

### Backfill warning

If a large historical backfill is loaded into a monitored table, the increment for that scan period will be far above normal. The model will flag this as an anomaly. If you plan a backfill, either mute the monitor during the load or acknowledge the resulting incident as expected behaviour.

### Group by not supported

Volume monitors do not support Group By. If you need volume tracking broken down by a column value, use a Custom SQL monitor with a `GROUP BY` clause.

### Low-volume tables

On tables with very few rows per period, the Volume monitor may hit the [sparse-data threshold](/data-quality/anomaly-detection-explained.md#sparse-data-and-silent-skipping) (fewer than 5 valid points in 30 observations) and silently skip scans. For low-volume tables, a manual threshold (Absolute or Percentage) is more reliable than Smart Training.

***

## Before you begin

* You need at least one data source connected and a table available under that source.
* To use Smart Training, the table must have a timestamp column (or you must provide an SQL expression that produces one).

***

## Step 1: Set up

1. In the **Data Quality** module, go to the **Config** tab and select **Create**.
2. Select the **Volume** monitor card.
3. In the **Create a New Monitor** form, select your **Source** (Schema is optional) and **Dataset**.
4. Choose **Monitor mode**: **Scheduled** or **On-Demand**.
5. Click **Proceed to Monitor Setup**.

***

## Step 2: Configure — Scheduled monitor

| Field                   | Description                                                                                                                                                                                   |
| ----------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Monitor Name**        | A descriptive name for this monitor.                                                                                                                                                          |
| **Monitor Description** | Optional.                                                                                                                                                                                     |
| **Row Creation**        | How Decube identifies new rows: **Timestamp** (select a timestamp column), **SQL Expression** (provide an expression that produces a timestamp), or **All Records**.                          |
| **Smart Training**      | Toggle on to train the model on historical increments. Requires Timestamp or SQL Expression.                                                                                                  |
| **Frequency**           | How often the monitor scans. See [Custom Scheduling for Monitors](https://github.com/DecubeIO/decube-docs/blob/public/data-quality/how-to-set-up-monitors/custom-scheduling-for-monitors.md). |
| **Incident Level**      | Severity assigned to incidents this monitor opens.                                                                                                                                            |

{% hint style="warning" %}
**All Records** mode does not support Smart Training and can produce incorrect deltas if rows are deleted. Use Timestamp or SQL Expression row creation whenever possible.
{% endhint %}

### SQL Expression

Use an SQL Expression when your table stores timestamps in a non-standard format. See the [SQL Expression examples on the Freshness setup page](/data-quality/how-to-set-up-monitors/set-up-freshness-monitors.md#sql-expression) for common conversion patterns. Validating the expression before saving is required.

### Notifications

Turn on **Notify default channel** to route incidents to a specific email or Slack channel. Click **Submit** to create the monitor.

***

## Step 2: Configure — On-Demand monitor

On-Demand monitors do not use Smart Training, Auto Threshold, or frequency scheduling.

| Field                   | Description                                        |
| ----------------------- | -------------------------------------------------- |
| **Monitor Name**        | A descriptive name.                                |
| **Monitor Description** | Optional.                                          |
| **Row Creation**        | **Timestamp** or **SQL Expression** only.          |
| **Lookback Period**     | The time window to check when the monitor runs.    |
| **Incident Level**      | Severity assigned to incidents this monitor opens. |

To finish:

* Click **Save** to create the monitor without running it immediately.
* Click **Save and Run** to create and run the monitor straight away.

After creation, you can run the monitor again from **All Monitors** by clicking the ellipsis (︙) and selecting **View Monitor**, then **Run once**.

***

## Related pages

{% content-ref url="/pages/YpzBR4Fms5X6aZfHSJXj" %}
[Set Up Freshness Monitors](/data-quality/how-to-set-up-monitors/set-up-freshness-monitors.md)
{% endcontent-ref %}

{% content-ref url="/pages/12tZSWlWRX4XEXBTD4L6" %}
[How Anomaly Detection Works](/data-quality/anomaly-detection-explained.md)
{% endcontent-ref %}

{% content-ref url="/pages/KgXixMx9V2joZYvvAjL9" %}
[Retraining Monitors](/data-quality/monitor-configuration-settings/retraining-monitors.md)
{% endcontent-ref %}