I recently had to troubleshoot a Problem where the Customer told me that sometimes all the Sessions on a XenApp 6 Host got disconnected and the Users then had to reconnect to their XenApp Sessions to continue working.

After a little Research (thanks to Google!) I narrowed it down to the the Group Policy Refresh. Not always, but sometimes, when doing an "gpupdate /force" on a XenApp Host all User Sessions got disconnected. With this in mind I found the following Microsoft Knowledgebase Article: http://support.microsoft.com/kb/2083411

The customer in fact used the Group Policy Option "Allow users to connect remotely using Terminal Services" to enable Remote Desktop and force a specific Remote Desktop Security Setting on all of his XenApp Servers.

After setting the Registry Key "fDenyTSConnection" to 0 (as suggested in the Microsoft KB Article) the sudden disconnects were gone.

Problem solved! :)

I recently worked in a Project where we deployed XenApp 6.5 Workers via Citrix Provisioning Services 6.0 (PVS) onto a vSphere 5 Cluster and ran into a Problem regarding the PXE Boot. We knew that PVS 6.0 is currently not supported with vSphere 5, but the customer wanted to use his vSphere 5 Cluster nonetheless.

Everytime we rebooted a Target Device, running an XenApp 6.5 Worker, it would reboot and then hang on the PXE Boot in a Screen like this:

When we powered the VM completely off and then started the VM again (cold reboot) the PXE Boot worked without a Problem. The Problem would only occur when rebooting the VM without completely shutting it down before (warm reboot).

To fix the Problem we enabled the "Interrupt safe mode" Option in the Bootsptrap Configuration of our Provisioning Servers:

And voilà: Rebooting the XenApp 6.5 Workers on a vSphere 5 Host/Cluster now works as expected.

UPDATE: Citrix published an official Support Article (with the same Solution) regarding the Bootstrap Configuration in an vSphere 5 Enviroment: http://support.citrix.com/article/CTX131993