> ## Documentation Index
> Fetch the complete documentation index at: https://docs.datachecks.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Validation Window

> Configure global or tumbling time windows to control how validation metrics are calculated.

Windows determine the scope of data that a validation runs against. Datachecks supports two window types: **Global** and **Tumbling**.

## Global windows

A global window runs the validation against the entire dataset on every execution. There is no time-based partitioning — every row in the table is included each time.

**Best for:** Small tables, or when you need a full-dataset view every run.

**Trade-offs:** On large tables, global windows perform a full data load on every polling cycle, which can cause performance degradation and high resource consumption.

No additional configuration is required for global windows.

***

## Tumbling windows

A tumbling window divides data into fixed, non-overlapping time segments based on a timestamp column. Each segment is validated independently, making it easier to identify issues in a specific batch or time period.

**Best for:** Large tables, continuous monitoring of recent data, identifying temporal anomalies, and batch-specific quality checks.

### Configuration parameters

| Parameter            | Description                                                                                  |
| -------------------- | -------------------------------------------------------------------------------------------- |
| **Date-Time Field**  | The timestamp column used to partition data into segments (e.g. `created_at`, `event_time`). |
| **Window Size**      | The length of each time segment, combined with Window Unit (e.g. `2` days).                  |
| **Window Unit**      | Unit for Window Size — `hours`, `days`, or `weeks`.                                          |
| **Look Back Period** | How far back in time to retrieve data, combined with Look Back Unit (e.g. `5` days).         |
| **Look Back Unit**   | Unit for Look Back Period — `hours`, `days`, or `weeks`.                                     |

### How it works

Given a Look Back Period of 10 days and a Window Size of 2 days, Datachecks creates 5 non-overlapping windows. Each window is validated independently. Only the data within the Look Back Period is considered — older records are excluded.

**Example:**

```
Look Back Period: 10 days
Window Size: 2 days

→ Window 1: days 1–2
→ Window 2: days 3–4
→ Window 3: days 5–6
→ Window 4: days 7–8
→ Window 5: days 9–10
```