Citrix Virtual Apps and Desktops

Upgrade a XenApp 6.5 worker to a new VDA

After you migrate a XenApp 6.5 farm, you can use your XenApp 6.5 servers that were configured in session-host only mode (also called session-only or worker servers) by removing the earlier software, upgrading the OS, and then installing a new VDA for Server OS.

Although you can upgrade a XenApp 6.5 worker server, installing the current VDA software on a clean machine provides better security.

To upgrade a XenApp 6.5 worker to a new VDA:

  1. Remove Hotfix Rollup Pack 7 for XenApp 6.5, using the instructions in the hotfix readme. See CTX202095.
  2. Uninstall XenApp 6.5. This process requires several restarts. If an error occurs during the uninstallation, check the uninstall error log referenced in the error message. That log file resides in the folder “%TEMP%\Citrix\XenDesktop Installation\XenApp 6.5 Uninstall Log Files\.”
  3. Upgrade the server’s operating system to a supported version. See the VDA for Server OS section in System requirements. for a list of supported platforms.
  4. Install a VDA for Server OS, using an installer provided with this release. See Install VDAs or Install using the command line.

After you install the new VDA, from Studio in the new XenApp Site, create machine catalogs (or edit existing catalogs) for the upgraded workers.


Removal of the XenApp 6.5 software fails. The uninstall log contains the message: “Error 25703. An error occurred while plugging XML into Internet Information Server. Setup cannot copy files to your IIS Scripts directory. Please make sure that your IIS installation is correct.”

Cause: The issue occurs on systems where (1) during the initial XenApp 6.5 installation, you indicated that the Citrix XML Service (CtxHttp.exe) should not share a port with IIS, and (2) .NET Framework 3.5.1 is installed.


  1. Remove the Web Server (IIS) role using the Windows Remove Server Roles wizard. (You can reinstall the Web Server (IIS) role later.)
  2. Restart the server.
  3. Using Add/Remove Programs, uninstall Citrix XenApp 6.5 and Microsoft Visual C++ 2005 Redistributable (x64), version 8.0.56336.
  4. Restart the server.
  5. Install the VDA for Server OS.
Upgrade a XenApp 6.5 worker to a new VDA