All Changes Revert Back After Reboot/Shutdown And BSOD (CtxMcsWbc.sys) in XenApp 7.11

Symptoms or Error

  1. VDA will randomly crash with BSOD.
  2. All changes in master image machine (with local HDD) will revert back after reboot/shutdown.


Cause 1: 
“PvsVmBoot” is missing from below mentioned registry location
Path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager
Name: BootExecute

Solution 1:

  1. Shutdown the VM.
  2. Boot the VM with Hiren’s Boot ISO (
  3. Launch Mini XP
  4. Edit registry with Registry Editor PE (Step 3:
  5. Expand below mentioned registry location and edit “BootExecute” registry string HKEY_LOCAL_MACHINE\REMOTE_SYSTEM\ControlSet001\Control\Session Manager

User-added image


  1. Verify the same under HKEY_LOCAL_MACHINE\REMOTE_SYSTEM\ControlSet002\Control\Session Manager
  2. Close Registry Editor
  3. Remove Hiren’s Boot CD from boot order and reboot the VM.


Cause 2:
CtxMcsWbc.sys Driver is not behaving as expected


NOTE: The workaround provided below with effectively disable this driver and leave the VDA in a state that is inconsistent.

This workaround may be used for troubleshooting, but will leave the VDA in an inconsistent state. This driver controls the MCS I/O  Optimization feature The full effect of disabling this driver is not clear at this point.


  1. Shutdown the VM.
  2. Boot the VM with Hiren’s Boot ISO (
  3. Edit registry with Registry Editor PE
  4. Disable the Citrix MCS cache service by changing the Start value from 0 to 4 from the following sub key:
  5. Delete the “CtxMcsWbc” entry in the “UpperFilters” value in the following sub key:
  6. Unload the System hive from the mounted VHD.
  7. Detach the mounted VHD.
  8. Start the VM  normally.

Upgrade to XenDekstop 7.15

Problem Cause

Issue with CtxMcsWbc.sys Driver.

Additional Resources

This is a known issue and has been fix in XenDesktop 7.14 [LC6488]

Affected version: XenDekstop 7.9 & 7.11

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Posted in: Server, VMWare