NEW - You can now accelerate your migration and modernization with AWS Transform. Read [Getting Started](https://docs.aws.amazon.com/transform/latest/userguide/getting-started.html) in the *AWS Transform User Guide*.

# Launching cutover instances
<a name="launch-cutover"></a>

Once you have finalized the testing of all of your source servers, you are ready for cutover. You should perform the cutover at a set date and time. The cutover migrates your source servers to the cutover instances on AWS. 

**Important**  
It is a best practice to perform a test at least two weeks before you plan to migrate your source servers. This time frame allows you to identify potential problems and solve them, before the actual migration takes place. After launching Test instances, use either SSH (Linux) or RDP (Windows) to connect to your instance and ensure that everything is working correctly. 

You can cutover one source server at a time, or simultaneously cutover multiple source servers. For each source server, you are informed of the success or failure of the cutover. For each new cutover, AWS Application Migration Service first deletes any previously launched Test instance and dependent resources. Then, it launches a new cutover instance which reflects the most up-to-date state of the source server. After the cutover, data replication continues as before. The new and modified data on the source server is transferred to the staging area subnet, and not to the cutover instances that were launched during the cutover.

**Topics**
+ [Ready for cutover indicators](ready-for-cutover.md)
+ [Starting a cutover](starting-cutover.md)
+ [Reverting a cutover](revert-finalize-cutover.md)
+ [Finalizing a cutover](finalizing-cutover-2.md)

# Ready for cutover indicators
<a name="ready-for-cutover"></a>

Prior to launching a cutover instance, ensure that your source servers are ready for cutover by looking for the following indicators on the **Source servers** page:

1. Under the **Migration lifecycle** column, the server should show **Ready for cutover** .

1. Under the **Data replication status** column, the server should show the **Healthy** status. 

1. Under the **Next step** column, the server should show **Terminate launched instance; Launch cutover instance** if you have not terminated your latest launched test instance.

1. Alternatively, the Next step column shows **Launch cutover instance** if you have terminated your latest launched test instance. 

# Starting a cutover
<a name="starting-cutover"></a>

To launch a cutover instance for a single source server or multiple source servers, go to the **Source servers** page and check the box to the left of each server you want to cutover. 

Open the **Test and cutover** menu.

Under **Cutover**, choose the** Launch cutover instances** option.

The **Launch cutover instances for X** servers dialog appears. Choose **Launch** to begin the cutover. 

In the **Source servers** page, the **Migration lifecycle** column shows **Cutover in progress** and the **Next step** column shows **Finalize cutover**. 

The AWS Application Migration Service console indicates **Launch job started** when the cutover has started. 

Choose **View job details** on the dialog to view the specific job for the cutover launch in the** Launch history** tab. 



## Successful cutover launch indicators
<a name="successful-cutover"></a>

You can tell that the cutover instance launch was started successfully through several indicators on the **Source servers** page.



1. The **Alerts** column displays **Launched**. 

1. The **Migration lifecycle** column displays **Cutover in progress**.

1. The **Data replication status** displays **Healthy**.

1. The **Next step column** displays **Finalize cutover**.

# Reverting a cutover
<a name="revert-finalize-cutover"></a>

Once you have launched your cutover instances, open the Amazon EC2 console and SSH or RDP into your cutover instances in order to ensure that they function correctly. Validate connectivity and perform acceptance tests for your application. 

**Note**  
You should turn on Termination Protection after you have completed your testing and before you are ready to finalize the cutover. Learn more about enabling termination protection in [this Amazon EC2 article](https://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/terminating-instances.html#Using_ChangingDisableAPITermination).

If you encounter any issues and want to launch new cutover instances, you can revert the cutover. This reverts your source servers' **Migration lifecycle** status to **Ready for cutover**, indicating that these servers have not undergone cutover. During a revert, you also have the option to delete your Cutover instances for cost-saving purposes.

To revert a cutover take the following steps:

1. Check the box to the left of every source server that has a launched cutover instance you want to revert.

1. Open the **Test and cutover** menu. 

1. Under **Cutover**, choose **Revert to "ready for cutover"**.

1. This reverts your source servers' **Migration lifecycle** status to **Ready for cutover**, indicating that these servers have not undergone cutover. 

   When the **Revert cutover for X servers** dialog appears, click **Revert**. 

# Finalizing a cutover
<a name="finalizing-cutover-2"></a>

If you are completely done with your migration and performed a successful cutover, you can finalize the cutover. This changes your source servers' **Migration lifecycle** status to **Cutover complete**, indicating that the cutover is complete and that the migration has been performed successfully. In addition, this stops data replication and causes all replicated data to be discarded. All AWS resources used for data replication are terminated. 

To finalize a cutover:

1. Check the box to the left of every source server that has a launched cutover instance you want to finalize.

1. Open the **Test and cutover** menu.

1. Under **Cutover**, choose **Finalize cutover**.

1. The **Finalize cutover for X servers** dialog appears. Choose **Finalize**. This changes your source servers' **Migration lifecycle** status to **Cutover complete**, indicating that the cutover is complete and that the migration has been performed successfully. In addition, this stops data replication and causes all replicated data to be discarded. All AWS resources used for data replication are terminated. 

   The AWS Application Migration Service console indicates **Cutover finalized** when the cutover has completed successfully. 

   The AWS Application Migration Service console automatically stops data replication for the source servers that were cutover in order to save resource costs. The selected source servers' **Migration lifecycle** column shows the **Cutover complete** status, the **Data replication** status column shows **Disconnected**, and the **Next step** column shows **Mark as archived**. The source servers have now been successfully migrated into AWS.

1. You can now archive your source servers that have launched cutover instances. Archiving removes these source servers from the main **Source servers** page, allowing you to focus on source servers that have not yet been cutover. You are still able to access the archived servers through filtering options. 

   To archive your cutover source servers:

   1. Check the box to the left of the of each source server for which the **Migration lifecycle** column states **Cutover complete**.

   1. Open the **Actions** menu and choose **Mark as archived**.

   1. When the **Archive X server** dialog appears, click **Archive**.

   1. To see your archived servers, open the **Preferences** menu by choosing the gear button.

      Toggle the **Show only archived servers** option and click **Confirm**.

      You are now be able to see all of your archived servers. Untoggle the **Show only archived servers** option to show non-archived servers.