# Deltas and Changes

### Keeping Your Data Up to Date

In active environments, it’s common for files to be added or updated during a migration. Movebot’s **Delta Migration** feature helps keep your destination up to date by copying **only the files that have been added or modified** since the last transfer.

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### How Delta Migrations Work

Delta Migrations compare the **source and destination** using each file’s **modification time (modtime)**.\
Only files that are **new** or have a **more recent modtime** on the source will be transferred. This reduces duplication and speeds up the process by skipping files that haven't changed.

> **Important:**\
> Movebot does **not delete or move** files at the destination.  \
> \
> If you rename, move, or delete files or folders in the source, those changes will **not** be reflected in the destination. \
> \
> To avoid duplication or confusion, we recommend avoiding major restructuring during the migration process.

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### Enabling "Always Use Delta"

To enable Delta Migrations across all runs:

1. Go to **Step 4** in your project settings.
2. Enable the **“Only Include Changed Files/Objects”** option.

This ensures Movebot will compare the source and destination before each transfer and skip any files that haven’t changed.\
Note: This option may increase **scan time**, but reduces **transfer time** by focusing only on what’s changed.

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### Running a Delta Migration Manually

You can manually launch a Delta Migration at any time. Here’s how:

1. Open your project.
2. Select the job(s) you want to run a Delta for.
3. Click **Launch Scan or Transfer**.
4. Choose **Start Delta Migration**.<br>

Delta runs may take slightly longer to scan but are **much faster during the transfer stage** than full migrations. They can be run as often as needed and are particularly helpful for:

* Catching files that were created or updated during a prior transfer
* Cleaning up certain error types, such as:
  * **Unknown errors**
  * **File-not-found**
  * **Checksum-mismatches**