When Windows Update installs updates, it uses the Kernel Transaction Manager (KTM) and Transactional NTFS (TxF) to manage file operations. If these components fail, the update process can't commit its changes. This error occurs if one of the following conditions exists:

• The TxF transaction log file on the system volume is corrupted.
• The KTM or TxF can't start or manage file transactions.
• A previous update didn't install correctly. This failure left the transaction subsystem in an inconsistent or bad state.
• Disk errors block access to the transaction log.
• An antivirus program or file system filter driver blocks transactional file operations.
• The Windows component store is corrupted.

Resolution: Troubleshoot Windows Update error 0x80071A91 untested here · 0 fixed, 0 not

Important

• Before you troubleshoot this issue, back up the operating system disk. For information about this process for virtual machines (VMs), see About Azure Virtual Machine restore.
• If the affected computer is a VM that can't start, go to step 7.

Step 1: Request a reset of the transaction logs

To reset the NTFS transaction logs, follow these steps:

1. Open an administrative Command Prompt window, and run the following command:

   fsutil resource setautoreset true C:\
   

2. Restart the computer. When Windows starts, it re-creates the transaction logs.

Step 2: Repair the component store

To repair the component store, run the following command at the command prompt:

DISM /Online /Cleanup-Image /RestoreHealth

Note

By default, DISM uses Windows Update as a repair source. For information about how to specify a different repair source, see Repair a Windows Image.

After you run this command, restart the computer, and try again to install the update. If it still doesn't install, go to step 3.

Step 3: Check system file integrity

To verify the integrity of the system files, run the following command at the command prompt:

sfc /scannow

If this command identifies issues, see Use the System File Checker tool to repair missing or corrupted system files.

After this command finishes without errors, restart the computer. Try again to install the update. If it still doesn't install, go to step 4.

Step 4: Reset Windows Update components

If the transaction error persists, reset all Windows Update components. At the command prompt, run the following commands:

net stop wuauserv
net stop bits
net stop cryptSvc

ren %windir%\SoftwareDistribution SoftwareDistribution.old
ren %windir%\System32\catroot2 catroot2.old

net start cryptSvc
net start bits
net start wuauserv

After you run these commands, restart the computer, and try again to install the update. If it still doesn't install, go to step 5.

Step 5: Check disk health

To check for disk issues, follow these steps:

1. On the affected computer, open a Command Prompt window, and run the following command:

   chkdsk C: /f
   

   The tool automatically repairs any problems that it finds.

   Important

   If the affected computer is an Azure VM, and you use the Azure portal to monitor and remediate disk health, go to the next step of this procedure. You still have to restart the VM that uses the disk.

2. After the tool finishes, restart the computer, and try again to install the update. If the update still doesn't install, take one of the following actions:

   • If the affected computer is a VM, go to step 6.
   • Contact Microsoft Support for assistance.

Step 6: Use the Run Command reset tool (Azure)

If the previous steps don't resolve the issue on an Azure VM, try the Azure VM Windows Update Reset Tool. You can run the tool directly from the VM's Azure portal page by using Operations > Run command. When you use this method, you don't have to sign in to the VM.

This tool resets the Windows Update servicing stack. This action clears memory-related lock states in the update agent.

After you run the tool, try again to install the update. If it still doesn't install, go to step 7.

Step 7: Use a repair VM (Azure)

If the reset tool doesn't fix the issue, or the VM can't start:

1. Create a repair VM by using Azure VM repair commands.

2. Attach the affected operating system disk to the repair VM.

3. To reset the NTFS transaction logs, follow these steps:

   1. Open an administrative Command Prompt window on the repair VM, and then run the following command:

      fsutil resource setautoreset true <Drive>:\
      

      Note

      In this command, <Drive> represents the drive letter of the affected operating system disk.

   2. Restart the computer. When Windows starts, it re-creates the transaction logs.

4. Make sure that you have an offline operating system image available, and then run the following command at the command prompt:

   DISM /Image:<Drive>:\ /Cleanup-Image /RestoreHealth
   

   Note

   • In this command, <Drive> represents the drive letter of the affected operating system disk.
   • By default, DISM uses Windows Update as a repair source. For information about how to specify a different repair source, see Repair a Windows Image.

5. Reattach the repaired disk to the original VM.

6. Try again to install the update. If the update still doesn't install, contact Microsoft Support for assistance.

Log how it went

(Enterprise subscription only)

Repair-WindowsComponentStore untested here · 0 fixed, 0 not

Repair the Windows component store. Runs DISM ScanHealth, CheckHealth and RestoreHealth, then sfc /scannow.

Reset-WindowsUpdateAgent untested here · 0 fixed, 0 not

Reset the Windows Update agent. Stops the update services, renames the SoftwareDistribution and catroot2 folders so Windows rebuilds them, and starts the services again.