> 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-v2/monitors.md).

# Monitors

A monitor is a recurring or manually triggered check Decube runs against a data asset.

## Monitors

A monitor is a recurring, or manually triggered, check that Decube runs against a data asset: a table, or in the case of Custom SQL, the result of a query you write. Without one in place, you usually learn about a data problem when a dashboard looks wrong or a report fails to add up, days after the underlying issue started.

### What a monitor does

Every monitor follows the same pattern, whatever it checks:

1. It runs on a **schedule**, or you trigger it manually.
2. It collects a **metric** relevant to what it checks, such as the age of the newest row, the number of rows, or the number of values that break a rule.
3. It evaluates that metric against the **Threshold** or **Tolerance** you configured.
4. If the evaluation fails, it raises an **incident**, and Decube files that incident under a case.

A Freshness monitor, for example, might run every hour, measure the age of the newest row in a table, and compare that age against the maximum you set. Once the data is older than that, the monitor raises an incident, and your alert rules decide who hears about it.

### Read Building blocks first

A handful of settings reappear across almost every monitor type: schedule, detection method, scan method, Threshold, Tolerance, custom attributes, and what counts as a destructive change. Building blocks explains each one setting once which makes every monitor type page faster to read.

{% content-ref url="/pages/cIdLEg3BGf44JgzD7UvJ" %}
[Building Blocks](/data-quality-v2/monitors/building-blocks.md)
{% endcontent-ref %}

### Then work through this section

For what each check does and what you configure on it, see [Monitor types](/data-quality-v2/monitor-types.md). To apply one configuration across many tables at once, see:

{% content-ref url="/pages/gTbg3448XNHbTM66M7h5" %}
[Create monitors in bulk with Templates](/data-quality-v2/create-monitors-in-bulk-with-templates.md)
{% endcontent-ref %}