NetWorker: SharePoint Backup Causes VSS Error with Event ID 8194

• SharePoint backup jobs complete but log the following error in the Windows Event Log:

  Error 11/11/2025 12:34:14 AM VSS 8194 None
  "Volume Shadow Copy Service error: Unexpected error querying for the IVssWriterCallback interface.
  hr = 0x80070005, Access is denied."
  

• Event ID: 8194
• Error code: 0x80070005 (Access Denied)

The error occurs because DCOM permissions for VSS-related service accounts are insufficient. This prevents VSS from querying the IVssWriterCallback interface during backup operations.

Update DCOM permissions on all SharePoint and SQL nodes:

Steps to Update DCOM Permissions.

1. Open Component Services:
   • Press Win + R, type dcomcnfg, and press Enter.
2. Navigate to:

   Component Services → Computers → My Computer → Properties → COM Security
   

3. Under Access Permissions → Edit Default:
   • Add NETWORK SERVICE → grant Local Access.
   • Add LOCAL SERVICE → grant Local Access.
4. Under Launch and Activation Permissions → Edit Default:
   • Add NETWORK SERVICE → grant Local Launch and Local Activation.
   • Add LOCAL SERVICE → grant Local Launch and Local Activation.
5. Apply the changes and restart the backup service if necessary.

After applying these settings, VSS Event ID 8194 (Access Denied) errors should no longer appear.

• Ensure that permissions are applied consistently across all nodes in the SharePoint farm and SQL servers.
• No reboot is typically required, but restarting backup services may help apply changes immediately.