This error may occur when copying open/locked files and the files and the system is overloaded. The possible solutions are:

  • This error may occur if you have other profiles running at the same time and they are also copying locked/open files
  • Close any unnecessary programs, or pause them
  • Defragment the partition the locked files are on (if it is a hard drive, not if using solid-state storage, e.g. an SSD)


By default SyncBackSE/Pro will wait a maximum of 5 minutes to be able to copy open/locked files from a drive. It is possible to change the amount of time to wait:

  • Run SyncBackSE/Pro
  • Select burger menu > Global Settings > Settings tab
  • Click on the path inside the group-box with the title The settings are stored here. A Windows File Explorer window will open.
  • Exit SyncBackSE/Pro now (it is vital that you now exit SyncBackSE/Pro, otherwise any changes made after this will not be saved)
  • In the Windows File Explorer window double-click on the file settings.ini
  • Go to the end of the file and add the following line:

VSSSleep=360000

  • Save the file and exit the editor. Now run SyncBackSE/Pro.
  • It will now wait 6 minutes for the VSS DLL to become available. The VSSSleep value is the number of milliseconds, so if you wanted it to wait 7 minutes, for example, you would set it to 420000


If you are still getting the same error then consider modifying the registry to tell Windows to use a larger area of the drive for VSS use:

  • Run the Windows registry editor (regedit.exe)
  • Navigate to the key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VolSnap\
  • Modify (or create) the DWORD value MinDiffAreaFileSize
  • The default size is 300 and the maximum is 3000. This is the minimum size (in megabytes) to use on a drive for VSS.
  • Reboot


Microsoft also recommends that the Windows event logs are kept below 64MB in size. You can clear them, or set their maximum size, using the Event Viewer in Windows.


Advanced VSS Options


SyncBackPro and SyncBackSE V12 (and later) include advanced Volume Shadow Copy Service (VSS) options that provide reliable copying of open or locked files. These settings allow administrators to select and fine-tune VSS components such as providers, context, and backup type to ensure compatibility with different storage environments and application requirements.


In most cases, the default configuration is sufficient. However, advanced options are available for scenarios that require specific snapshot behavior or integration with enterprise storage systems, such as enterprise RAID systems or SAN arrays. For example, a SQL database VSS provider can ensure that database files are captured in a consistent and complete state during the copy process.


You can access the advanced VSS options from Modify Profile > Expert > Copy/Delete > VSS Settings.