Avamar: Backup Fails with "Windows Structured Exception ACCESS_VIOLATION" Errors

Summary: This article explains the causes and resolutions for Avamar backup failures that report Windows structured exception ACCESS_VIOLATION errors. These errors typically occur during Windows file system backups and may involve issues with Office XML files, outdated client versions, or antivirus interference. ...

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Symptoms

  • File system backups fail with ACCESS_VIOLATION errors in the logs.

 

  • Example log entries:    

  
ERROR: nbackmain - Windows structured exception ACCESS_VIOLATION in threadID 3656
ERROR: threadimpl::runthread() - Windows structured exception ACCESS_VIOLATION in threadID 8380

        
Cause

        

   ACCESS_VIOLATION errors can occur due to:
  

  
    
   
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     Avamar attempting to inflate Office XML files during backup
    
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     Windows client software running an older version than the Avamar grid
    
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     Antivirus software locking files during backup
    
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     Other client-specific issues (such as, Hyper-V, SQL backups)
    
    • 
  

        
Resolution

        

   1. Disable Office XML Inflation:
  

  
    
   
  • 
    
    
     Create an avtar.cmd file in the "C:\Program Files\avs\var" directory. 
    
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     Add the following flag:
    
    
    
    --inflateofficexml=false
    
    
    
     (This prevents Avamar from decompressing Office XML files before backing them up.)
    
    • 
  

  

    
  

  

   2, Update Avamar Client Software:
  

  
    
   
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       Ensure that the Windows client version matches the latest version available on the Avamar grid
      
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       Download updates from the Avamar server’s Documents and Downloads page
      
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   3. Check Antivirus Interference:
  

  
    
   
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       Verify that antivirus scans do not overlap with scheduled backups
      
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       Exclude Avamar processes or backup directories from real-time antivirus scanning if necessary
      
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   4. Escalate if the issue persists:
  

  
    
   
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       For unresolved cases, contact Dell Support and reference this knowledge article
      
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Affected Products

        Avamar, Avamar Client for Windows







                        

                            

    

        

            

                
                    
 Article Properties

                
            

            

                

                        
Article Number: 000039562

                

                
                

                        
Article Type: Solution

                

                

                        
Last Modified: 12 يناير 2026


                

                    

                            
Version:  6

                    


            


        

    

    

        

            

                
                    
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