SharePoint Large File Library Via Windows Explorer – Error

This is a post moved over from my old blog — still relevant.

Recently, I had the opportunity to take a look at an issue with accessing SharePoint file libraries through Windows Explorer UNC shares.  When those file libraries have HUGE numbers of files, the client will hang for upwards of five minutes and then error out with the following error:

“[\\UNCLocation\] is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions.  A device attached to the system is not functioning.”

Frustrating right?

Before I get to the fix, lets review the why.  When you open a folder on a Windows system (remote or local), the system has to do a couple of things:

  1. Obtain a listing of all the objects in the folder.
  2. Pull the attributes for every file.
  3. Display the files.

Well, in this case, the number of files pushes the limit of the attributes that the Windows system can load at one time due to restrictions put in place to prevent Denial of Service attacks on WebDAV Clients.  This can also happen when you are downloading VERY LARGE single files due to the same type of restrictions.

The Fix:

For Large File Libraries:

  1. Open Regedit & Go Here: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters\
  2. Edit the “FileAttributesLimitInBytes” value from 1000000 to 20000000

For Opening Large Files:

  1. Open Regedit & Go Here: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters\
  2. Edit the “FileSizeLimitInBytes” value to anything larger than the file you intend to download.  The default value is 50000000.