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:


  • 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.