Troubleshooting VSS Error: Resolving 'CoCreateInstance' Failures in Volume Shadow Copy Service

Table of Contents

• Resolving VSS Error: Unexpected error calling routine CoCreateInstance, Event ID 8193¶
• Conclusion¶

Encountering errors related to the Volume Shadow Copy Service (VSS) can be a significant concern for system stability and data protection. One specific error, often logged in the Windows Event Viewer as Event ID 8193, indicates an “Unexpected error calling routine CoCreateInstance”. This error is crucial because VSS is the underlying technology used by many backup, system restore, and imaging applications to create snapshots of files or volumes, even while they are in use. A malfunctioning VSS can prevent successful backups, leading to potential data loss in the event of a system failure.

The error message commonly associated with Event ID 8193 and CoCreateInstance failure might look like this:

Volume Shadow Copy Service error: Unexpected error calling routine CoCreateInstance. hr = 0x8007045b, A system shutdown is in progress.

While the appended message “A system shutdown is in progress” might suggest a temporary state, the CoCreateInstance failure part points to a more fundamental issue with COM (Component Object Model) or VSS component registration and accessibility. CoCreateInstance is a Windows API function used to create an instance of a COM object, which VSS heavily relies on for its operations. A failure here suggests the necessary VSS components or related system objects cannot be properly initialized or accessed by the service or calling application. This can stem from various causes, including service misconfiguration, corrupted system files, permission issues, or problems with VSS components themselves.

Resolving the VSS Error, Unexpected error calling routine CoCreateInstance, Event ID 8193 requires a systematic approach to address potential root causes. The following methods outline common troubleshooting steps that can help diagnose and fix this specific VSS problem. These steps range from verifying basic service status to repairing core system components, covering the most likely culprits behind CoCreateInstance failures within the V VSS framework.

Resolving VSS Error: Unexpected error calling routine CoCreateInstance, Event ID 8193¶

If you are facing the VSS Error with Event ID 8193 indicating an unexpected error calling CoCreateInstance, the following solutions should be applied methodically. Each step targets a different potential layer of failure within the VSS ecosystem, aiming to restore its proper functionality.

Here are the primary troubleshooting steps to consider:

1. Check VSS Service Status and Configuration
2. Re-register Essential VSS Components
3. Verify Network Service Account Permissions on Registry Keys
4. Repair System Image and Corrupted Files
5. Evaluate Disk Space and Shadow Copy Storage Limits
6. Check for Software Conflicts (Antivirus, Backup Software)
7. Examine VSS-Related Event Logs for More Clues

Let’s explore each of these solutions in detail to understand the process and underlying reasons why they are effective.

1] Check VSS Service Status and Configuration¶

The Volume Shadow Copy Service (VSS) itself must be running and configured correctly for any shadow copy operation to succeed. VSS coordinates the activities of VSS writers (applications like databases or mail servers), VSS providers (components that interface with the file system or storage), and VSS requestors (applications initiating the backup or snapshot). If the core VSS service is stopped, disabled, or experiencing startup issues, it cannot orchestrate these components, leading to failures like the CoCreateInstance error when a requestor attempts to interact with it.

The first step in troubleshooting is to ensure the VSS service is operational and set to start automatically. This fundamental check eliminates a simple yet common cause of VSS-related problems.

To check and configure the VSS service status:

1. Open the Services application. You can do this by typing services.msc in the Run dialog (Windows Key + R) or searching for “Services” in the Start Menu.
2. In the Services window, scroll down the list to find the Volume Shadow Copy service.
3. Right-click on the Volume Shadow Copy service and select Properties.
4. Examine the Startup type. It should ideally be set to Automatic or Automatic (Delayed Start). If it is set to Manual or Disabled, change it to Automatic (Delayed Start) to ensure it starts correctly after the system boots, allowing other necessary services to initialize first.
5. Check the Service status. If the status is Stopped, click the Start button.
6. Click Apply and then OK to save the changes.

If the service was already running, right-clicking the service and selecting Restart can help resolve temporary glitches. After making any changes or restarting the service, it’s recommended to reboot your computer. Once the system is back online, check the Event Viewer again after some time (perhaps after a scheduled backup attempt or manually triggering one) to see if Event ID 8193 persists. You can filter the Application log in Event Viewer by Source: VSS to isolate related events. Success events or the absence of the error indicate that the issue might be resolved.

It’s also beneficial to check the dependencies of the Volume Shadow Copy service within its Properties window (Dependencies tab) to ensure that the services it relies upon are also running and configured correctly. Common dependencies include the Remote Procedure Call (RPC) service and the COM+ Event System service, which are fundamental to inter-process communication and COM object activation.

2] Re-register Essential VSS Components¶

The CoCreateInstance error specifically points to a failure in creating a COM object instance. VSS relies on several COM components, implemented as DLL (Dynamic Link Library) files, to function correctly. If these DLLs become unregistered, corrupted, or are missing from the system’s registration database, the CoCreateInstance calls originating from VSS or applications interacting with VSS will fail. Manually re-registering these core VSS-related DLLs using the regsvr32 command can refresh their entries in the system registry, ensuring they are properly recognized and available for use by COM.

This process involves executing specific commands in an elevated Command Prompt. It’s a common step for resolving issues where system components fail to initialize or communicate properly.

To re-register VSS components:

1. Open the Command Prompt as an administrator. The easiest way is to search for “cmd” in the Start Menu, right-click on “Command Prompt”, and select “Run as administrator”. Confirm the User Account Control (UAC) prompt if it appears.

2. In the Administrator: Command Prompt window, execute the following commands one by one. Press Enter after typing each command and wait for a confirmation message (e.g., “DllRegisterServer in [DLL name] succeeded.”) before proceeding to the next.

   regsvr32 ole32.dll
   regsvr32 vss_ps.dll
   regsvr32 /i swprv.dll
   regsvr32 /i eventcls.dll
   regsvr32 es.dll
   regsvr32 stdprov.dll
   regsvr32 vssui.dll
   regsvr32 msxml.dll
   regsvr32 msxml3.dll
   regsvr32 msxml4.dll
   

   • regsvr32: The command-line utility to register and unregister DLLs and ActiveX controls in the Windows registry.
   • /i: This flag is used with regsvr32 to call DllInstall during the registration process, which performs installation-specific tasks in addition to registration. It’s used for swprv.dll (Microsoft Software Shadow Copy Provider) and eventcls.dll (COM+ Event System).
   • The listed DLLs are crucial for various aspects of VSS functionality, COM operations (like ole32.dll), VSS providers (swprv.dll, stdprov.dll), the COM+ Event System (eventcls.dll, es.dll), VSS user interface components (vssui.dll), and XML parsing components (msxml.dll, msxml3.dll, msxml4.dll) often used by applications interacting with VSS.

3. After executing all the commands, close the Command Prompt.

4. Reboot your computer. A restart is necessary for the changes to the registry to take full effect and for services to load the components correctly.

After the system restarts, attempt the operation that previously caused the VSS error or check the Event Viewer again for new VSS logs. If the issue was due to unregistered or improperly registered VSS components, this step should resolve the CoCreateInstance failure.

3] Verify Network Service Account Permissions on Registry Keys¶

In some cases, VSS operations can fail due to insufficient permissions for the system accounts under which VSS components or related services run. A common permission-related VSS error (also Event ID 8193) mentions “Access is denied”. Although our specific CoCreateInstance error might not explicitly state “Access is denied”, insufficient permissions can still prevent the successful instantiation of COM objects needed by VSS. Specifically, issues with the permissions for the NETWORK SERVICE account on the VSS\Diag registry key have been known to cause VSS problems. The Diag key is used by VSS for logging or diagnostic purposes, and restricted access for critical service accounts can disrupt operations.

By ensuring the NETWORK SERVICE account has the necessary permissions on the Diag registry key, we can rule out a common cause of access-related failures that might manifest as a CoCreateInstance error.

Caution: Modifying the Windows Registry carries risks. Incorrect changes can cause system instability or prevent Windows from starting. It is highly recommended to back up the registry before making any modifications. You can usually do this within the Registry Editor itself by going to File > Export and saving a .reg file.

To check and modify permissions for the NETWORK SERVICE account on the VSS Diag key:

1. Open the Registry Editor. Search for “regedit” in the Start Menu or type regedit in the Run dialog (Windows Key + R) and press Enter. Confirm the UAC prompt if it appears.
2. Navigate to the following registry key:
   Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VSS\Diag
   You can copy and paste this path into the address bar at the top of the Registry Editor window and press Enter.
3. Right-click on the Diag folder (key) in the left-hand pane and select Permissions….
4. In the Permissions window, click the Add… button.
5. In the “Select Users, Computers, Service Accounts, or Groups” dialog, type NETWORK SERVICE in the “Enter the object names to select” field and click Check Names. The name should resolve and become underlined. Click OK.
6. Back in the Permissions window, select the NETWORK SERVICE entry in the list of Group or user names.
7. In the “Permissions for NETWORK SERVICE” box, ensure that the Allow checkbox for Full Control is checked. If it’s not checked, tick the box.
8. Click Apply and then OK to save the permission changes.
9. Close the Registry Editor.

After adjusting the registry permissions, you must reboot your computer for these changes to take effect and influence how the NETWORK SERVICE account interacts with the specified registry key. After the reboot, check if the VSS error persists during backup or snapshot operations.

4] Repair System Image and Corrupted Files¶

Core system files and components provide the foundation for services like VSS. If the Windows system image is corrupted or essential system files are missing or damaged, it can directly impact the functionality of VSS and its ability to instantiate COM objects. The System File Checker (SFC) and Deployment Image Servicing and Management (DISM) tools are built-in Windows utilities designed to scan for and repair corrupted system files and the Windows component store.

Running SFC and DISM scans can identify and fix underlying operating system issues that might be contributing to the VSS CoCreateInstance error. sfc /scannow specifically checks protected system files, while DISM is used to repair the Windows image itself, which is the source for files SFC might need to replace.

To repair your system image and corrupted files:

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1. Open the Command Prompt as an administrator. Search for “cmd”, right-click, and select “Run as administrator”.

2. Run the following command to scan and attempt to repair protected system files. This process can take some time.

   sfc /scannow
   

   Wait for the scan to complete. It will report whether it found and repaired any issues.
   3. After the SFC scan finishes, run the following DISM commands. These commands check the health of the Windows component store and attempt to restore it if issues are found. These also require an active internet connection to download necessary files from Windows Update if local copies are corrupted.

   Dism /Online /Cleanup-Image /ScanHealth
   

   
   This command scans the image for any corruption.

   Dism /Online /Cleanup-Image /CheckHealth
   

   
   This command quickly checks if an image is repairable (flags if corruption was previously detected).

   Dism /Online /Cleanup-Image /RestoreHealth
   

   
   This command scans the image for corruption and performs a repair operation automatically using Windows Update as the source for files. This is the most comprehensive repair command.

   Run each DISM command one by one, waiting for each to complete before starting the next. The RestoreHealth command, in particular, can take significant time.

3. Once all commands have completed, close the Command Prompt.

4. It is advisable to reboot your computer after running these repair tools, especially if issues were found and fixed.

After the system restarts, test the VSS functionality again. If the CoCreateInstance error was caused by corrupted system files or an unhealthy component store, the SFC and DISM repairs should resolve the issue.

5] Evaluate Disk Space and Shadow Copy Storage Limits¶

While the CoCreateInstance error message doesn’t explicitly mention disk space, insufficient space can sometimes indirectly lead to VSS failures or mask the true underlying problem. VSS requires space to store shadow copies (snapshots) of the volumes. If the allocated storage area for shadow copies is full or the volume itself is critically low on free space, VSS operations, including the initial stages involving COM object creation, might fail unexpectedly.

Furthermore, one of the common reasons for a general VSS unexpected error (as mentioned in the FAQ from the source article) is indeed lack of disk space for shadow copies. Although the error message might vary, it’s a vital area to check for any VSS issue.

To check disk space and VSS storage limits:

1. Check the free space on the drive where you are trying to create a shadow copy or backup. Ensure there is ample free space (Microsoft recommends at least 15% free space on volumes).
2. Check the current VSS storage allocation. You can do this using the vssadmin command-line utility in an administrator Command Prompt:
   

   vssadmin list shadowstorage
   

   
   This command shows how much space is used, allocated, and the maximum limit set for shadow copies on each volume.
3. If the “Used Shadow Storage Space” is close to or at the “Maximum Shadow Storage Space”, or if the maximum is very small, you may need to increase the limit. You can resize the allocation using the vssadmin resize shadowstorage command. For example, to set the maximum size for volume C: to 20GB, you would use:
   

   vssadmin resize shadowstorage /For=C: /On=C: /MaxSize=20GB
   

   
   You can specify the size in KB, MB, GB, TB, PB, or EB. Setting MaxSize=UNBOUNDED allows VSS to use up to 10% of the volume’s free space, adjusting dynamically.
4. Consider deleting old shadow copies if they are consuming too much space:
   

   vssadmin delete shadows /For=C: /All
   

   
   (Use with caution as this deletes all shadow copies on the specified volume). Or delete oldest ones:
   

   vssadmin delete shadows /For=C: /Oldest
   

Ensuring sufficient space for VSS operations is a crucial preventative measure and troubleshooting step that can resolve various VSS-related issues, including potential CoCreateInstance failures caused by resource exhaustion or related internal VSS states.

6] Check for Software Conflicts (Antivirus, Backup Software)¶

Third-party software, especially security programs like antivirus suites or other backup/imaging applications, can sometimes interfere with the Volume Shadow Copy Service. Antivirus programs might aggressively monitor or lock files, while conflicting backup software might try to use VSS exclusively or have incompatible components. This interference can prevent VSS from properly initializing its components or accessing necessary resources, leading to errors like CoCreateInstance failure.

To check for software conflicts:

1. Temporarily disable your antivirus software. Try running the VSS-dependent operation again. If it succeeds, the antivirus might be the culprit. You might need to configure your antivirus settings to exclude certain VSS processes or files, or consult the antivirus vendor’s support. Remember to re-enable your antivirus afterward.
2. If you have multiple backup or imaging applications installed (or remnants of previously uninstalled ones), try temporarily uninstalling any non-essential or potentially conflicting software. Reboot and test VSS again.
3. Check the documentation or support websites for your specific backup software or antivirus program for any known compatibility issues with VSS or specific Windows versions.

Identifying and resolving software conflicts is often done through a process of elimination. Temporarily disabling or uninstalling suspicious applications one by one can help pinpoint the source of the interference.

7] Examine VSS-Related Event Logs for More Clues¶

The initial problem might be flagged by Event ID 8193, but the Event Viewer often contains a wealth of related information that can point to the root cause. Other VSS-related event IDs logged around the same time as the 8193 error can provide more specific details about what went wrong during the VSS operation. For instance, events from VSS writers, providers, or the VSS service itself (Source: VSS) might indicate why the CoCreateInstance call failed – perhaps a specific writer wasn’t ready, a provider reported an error, or there was a timeout.

To get more diagnostic information from Event Viewer:

1. Open Event Viewer (search for “Event Viewer” in the Start Menu).
2. Navigate to Windows Logs > Application.
3. In the Actions pane (usually on the right), click Filter Current Log….
4. In the Filter dialog, under “Event sources:”, select VSS.
5. You can also specify “Event IDs:” to look for common VSS error IDs such as 12289 (Provider Error), 22 (Writer Error), 8193 (our target error), 13 (VSS Service Error), or others that appear frequently. However, initially filtering by just “VSS” source and sorting by date/time is often best.
6. Click OK to apply the filter.
7. Examine the events that occurred around the time the 8193 error was logged. Look for preceding or accompanying errors or warnings from VSS or related sources (like volmgr, disk, or application-specific sources if an application initiated the VSS call).

Analyzing these related event logs can offer critical clues. For example, if a specific VSS writer (like the System Writer, SQL Writer, Exchange Writer, etc.) is reporting errors just before the CoCreateInstance failure, the issue might lie with that specific application’s VSS component. Troubleshooting would then focus on that writer (e.g., checking its service status, re-registering it if possible).

Understanding the sequence and nature of other VSS events can significantly narrow down the potential causes of the CoCreateInstance failure and guide you towards the most effective solution.

Understanding VSS Components: Writers, Providers, and Requestors¶

To fully appreciate the complexity of VSS issues, it’s helpful to understand its architecture. VSS involves three main parties:

• VSS Requestors: These are applications that initiate the shadow copy process. Examples include Windows Backup and Restore, System Restore, third-party backup software, and even applications like SQL Server or Exchange that need to back up their own data consistently.
• VSS Writers: These are components within specific applications (like databases, mail servers, operating system services) that guarantee a consistent state of the application’s data during the shadow copy process. They prepare the data for snapshotting and freeze/thaw I/O operations briefly. When a writer isn’t functioning correctly, it can halt the VSS process.
• VSS Providers: These are components that actually create and maintain the shadow copies. Windows includes a default “Software” provider (swprv.dll), but hardware vendors or third-party software can provide their own “Hardware” or “Software” providers. Providers manage the storage space and the creation/deletion of snapshots.

The VSS service acts as the coordinator, receiving requests from Requestors, communicating with Writers to prepare data, and instructing Providers to create the shadow copy. A CoCreateInstance failure can occur at various points in this process if the necessary COM objects representing writers, providers, or core VSS interfaces cannot be instantiated. This highlights why troubleshooting needs to cover the service itself, its registered components, and the environment it operates within (permissions, system files, resources).

Conclusion¶

The VSS Error: Unexpected error calling routine CoCreateInstance, Event ID 8193, can be a frustrating issue, often preventing crucial backup and recovery operations. However, by systematically applying the troubleshooting steps outlined above, you can address the most common causes, ranging from simple service configuration problems and component registration issues to more complex permission problems and underlying system file corruption.

Begin with the basics: ensure the VSS service is running correctly. Then, proceed to re-register critical components to fix potential registry inconsistencies. Address permission issues for essential service accounts. Utilize system file checkers to rule out corruption as a factor. Always consider external influences like disk space limitations and conflicts with other software. Finally, leverage the wealth of information available in the Event Viewer to gain deeper insights into the specific circumstances surrounding the error.

Resolving this VSS error is vital for maintaining the integrity of your data protection strategy. By following these steps, you should be well-equipped to diagnose and fix the issue, ensuring your system can create reliable shadow copies when needed.

Did these steps help you resolve the VSS CoCreateInstance error? Do you have any other tips or experiences to share regarding this specific issue? Please leave your comments and feedback below!