*Applies to:* Windows Server 2022, Windows Server 2019, Windows Server 2016
## Introduction
This article describes methods that you can use to merge checkpoints into a virtual machine (VM) if Hyper-V has generated many differencing disks. The method that you use depends on the details of the situation.
## Merging checkpoints that you can view in Hyper-V Manager
Checkpoints that you can view in Hyper-V Manager are the simplest to handle. Usually, you can use the **Delete Checkpoint** command on the context menu to delete these checkpoints.
In some cases, **Delete Checkpoint** and **Delete Checkpoint Subtree** don't appear on the context menu. This can occur if third-party backup software generates checkpoints but doesn't delete them after a backup operation.
In these cases, you can still use the Delete key to delete the checkpoint.
In summary, to delete checkpoints in Hyper-V Manager (and merge the differencing disk files), follow these steps:
1. In Hyper-V Manager, select the virtual machine.
2. In the **Checkpoints** list, right-click the checkpoint that you want to delete, and then take one of the following actions:
- Select **Delete Checkpoint**.
- If **Delete Checkpoint** isn't available, select the checkpoint, and then select **Del**.
## Merging checkpoints that you can't view in Hyper-V Manager
You might encounter a situation in which Hyper-V Manager doesn't show checkpoints for a specific VM. At the same time, the corresponding file system folder shows many differencing disk files. This can occur if third-party backup software generates checkpoints but doesn't delete them after a backup operation.
You can merge the differencing disk files in one of two ways, depending on whether you can shut down the VM.
### When you can shut down the VM
To merge the differencing disk files, shut down the VM. Typically, the differencing disk files merge as part of the VM shutdown process.
### When you can't shut down the VM
You can merge differencing disks into an online VM. However, this is a multi-step process that involves Windows PowerShell scripts. To do this, follow these general steps:
1. Back up all the differencing disk files (VHD files).
2. [Create and run the `Get-VHDChain` function](https://learn.microsoft.com/en-us/troubleshoot/windows-server/virtualization/merge-checkpoints-with-many-differencing-disks#getchain). This step is described in detail later in this section.
3. [Create and run merge commands](https://learn.microsoft.com/en-us/troubleshoot/windows-server/virtualization/merge-checkpoints-with-many-differencing-disks#mergechain). This step is described in detail later in this section.
4. Change the VM settings to point to the merged parent VHD.
5. Start the VM. A successful startup means that the merge completed successfully.
#### Create and run the Get-VHDChain function
PowerShell
```
function Get-VHDChain {
[CmdletBinding()]
param(
[string]$ComputerName = $env:COMPUTERNAME,
[string[]]$Name = '*'
)
try {
$VMs = Get-VM -ComputerName $ComputerName -Name $Name -ErrorAction Stop
}
catch {
Write-Warning $_.Exception.Message
}
foreach ($vm in $VMs){
$VHDs = ($vm).harddrives.path
foreach ($vhd in $VHDs){
Clear-Variable VHDType -ErrorAction SilentlyContinue
try {
$VHDInfo = $vhd | Get-VHD -ComputerName $ComputerName -ErrorAction Stop
}
catch {
$VHDType = 'Error'
$VHDPath = $vhd
Write-Verbose $_.Exception.Message
}
$i = 1
$problem = $false
while (($VHDInfo.parentpath -or $i -eq 1) -and (-not($problem))){
If ($VHDType -ne 'Error' -and $i -gt 1){
try {
$VHDInfo = $VHDInfo.ParentPath | Get-VHD -ComputerName $ComputerName -ErrorAction Stop
}
catch {
$VHDType = 'Error'
$VHDPath = $VHDInfo.parentpath
Write-Verbose $_.Exception.Message
}
}
if ($VHDType -ne 'Error'){
$VHDType = $VHDInfo.VhdType
$VHDPath = $VHDInfo.path
}
else {
$problem = $true
}
[pscustomobject]@{
Name = $vm.name
VHDNumber = $i
VHDType = $VHDType
VHD = $VHDPath
}
$i++
}
}
}
}
==================================
```
This script defines a `Get-VHDChain` function that identifies the VHD chain (the set of differencing disks for the VM).
3. Run the following command:
PowerShell
```
Get-vhdchain -name PowerShell
```
$vm = Read-Host("please enter the VMname")
```
3. At the command prompt, enter the virtual machine name.
4. Copy the following script, and then paste it at the command prompt.
PowerShell
```
$vhds=Get-VM $vm | Select-Object -Property VMId | Get-VHD
if (Test-Path '.\merge.txt'){Remove-Item -Path '.\merge.txt'}
foreach($vhd in $vhds){
$chain=[ordered]@{}
while ($vhd.ParentPath){
$chain.add($vhd.Path,$vhd.ParentPath)
$vhd=Get-VHD -Path $vhd.ParentPath
}
$chain.GetEnumerator() | ForEach-Object {
$line='Merge-VHD -Path "{0}" -Destination "{1}"' -f $_.key, $_.value
$line | Out-File -FilePath .\merge.txt -Append
}
}
```
The script should resemble the following script:
2. Open *C:\\temp\\merge.txt*. This file contains a list of command line commands that are grouped into pairs. Each pair of commands defines the merge operations for a single differencing disk.
3. Copy the first command of the first pair, paste it at the command prompt, and then run it. Then, do the same for the second command of the first pair. These operations merge the differencing disk that the commands address.
4. After the disk merges, repeat the preceding steps for the next differencing disk in the list. Continue for all the differencing disks that the *merge.txt* file addresses.