Windows 2019 based Xenapp VDA in "Maximized" mode freezes upon or shortly after login if an Nvidia grid vgpu is present


I thought I’d throw this into the group. After months of suffering from an occasional bug where people’s Citrix sessions seem to freeze I have been able to deduce the cause down to something related to the gpu acceleration. If I for instance edit one of the Vmware VDA machines and remove the gpu this problem does not happen at all anymore on that server. It also only happens when the user uses his Citrix Xenapp session in “Maximized” mode. The combination of these 2 factors seem to trigger it.

Also interesting to note is that whenever the screen at the end user laptop or pc seems to freeze (like a glass screen you see a frozen picture of the current/latest screenrefresh) there is in reality no problem on the backend VDA server. The session never froze there or showed any hickup or error. As such a simple confirmed workaround is disconnect+reconnect to the session.

So in summary this mystery feels like the Citrix is trying to switch codec or something similar in order to activate gpu acceleration and freezed at that point.

ps: of course I have opened a Citrix case as well but I thought I would work both fronts as people here might have this problem too or recognise it.


Can you give some more details about the versions you are using?

Citrix VDA,
Grid software.

Can you also look at your Citrix policies that you enable GPU and also within your Windows RDS policy that you enable GPU. Please look at this:
GPU acceleration for Windows multi-session OS



Hi Sjoerd,

I noticed I wrongfully noted 2016 as OS. We are using Windows Server 2019 in fact.
The problem behaviour was succesfully reproduced on VDA’s 1912, 1912 CU2 and 2012.
Hypervisor= VMware ESXi, 7.0.0, 15843807 running on HP ProLiant DL380 Gen10 with Nvidia T4 Adapters
Grid ESXi software = NVIDIA-SMI 450.89 Driver Version: 450.89 CUDA Version: N/A
Client side software driver= version 452.57 (inside the Windows server 2019 VDA server build)

I’m checking your article in the meantime


I have a similar issue, except it does not only happen in fullscreen.

If a user is running a windowed desktop session it freezes after a few minutes.

Discconecting the session and reconnect to it and everything is working again (for a few minutes)

Any news on that issue?

Hi DiC,
which Citrix VDA are you using? Sounds like a Citrix issue or are you running at a resource limit (CPU load or FB exhaust)?



We are using 1912 LTSR CU2

And i don‘t think it is a resource issue.

It happens when only one session is connected to the server, just logged in to the desktop and doing nothing (CPU and GPU load is at 0-2%)

I have further investigated this issue and it’s getting weird:

The session isn’t realy freezing, it is just extremly (!) slow.
The clock in the taskbar of the session is running, but for 1 minute to run it takes about 10 to 20 minutes in realtime.
If i right-click the taskbar it takes minutes (!) to open the menu.

Disconnect and reconnect to the same session helps, but just for a few minutes and the problem reappears…


sorry but it sounds like your issue is nothing like the one I’m experiencing. You see in my issue nothing freezes on the server side nor becomes slow. In fact everything works fine on the server side whenever the end user experiences the “glass screen” effect so whatever it is is confined to the front end GUI experience so that sounds like a Citrix workspace app issue although it’s clearly dependent on the presence of a Nvidia vGPU adapter in the server side VDA.

I get it upon new logons but also reconnects to existing sessions but the issue only happens for sessions in maximized mode, never in fullscreen mode.

I was able to capture the and trace the issue both on client and server side. Citrix support is processing the trace logs right now as part of the case I have open.