One of the most unique features in our App Layering technology is our Elastic Layers for XenApp. In most layering technologies, XenApp or RDSH is “supported” by simply assigning a layer to the machines and exposing its content (applications) to every user session on that server. In Citrix App Layering, you can still assign a layer to a machine, but we also allow you to assign apps to users and groups, even in XenApp multi-user environments, providing real time delivery of the app right into their XenApp session.

This process starts at login, after authentication (but before profile load) and the layer assignments are found for that user. The layers (the actual VHDs that contains the layers) are then located and mounted as a volume inside the guest. Once mounted, the file system and registry are blended and presented to the user.

When this takes place in a XenApp server, this process is the same, but with one exception. The contents of these layers are exposed only to that user’s session. No other user logged into that session host will see the application unless they also have been assigned that same application and version.


This ability allows IT organizations to further reduce the number of images in an environment and allows for additional applications to be brought into the XenApp world without the additional management pain of standing up new silos. From a user’s perspective, this flexibility allows for a very personal experience as their applications (whether departmental or just one-offs assigned to them) can be dynamically loaded into their session.

So, what happens if multiple users are using the same app layer on a XenApp Server?

First note that all of these App Layers are mounted read only. This allows for sharing of the same VHDs not only within the same server but across multiple servers or silos. Second, once the assignments for a user are found the layering services will do is check to see if the requested layers are already present (mounted) on the VM. If the layer is found, that user is simply “authorized” to see the virtual registry and file system data. Once the user is logged in, they will see that application, just as other authorized users see it but without having to re-mount the VHD. If a layer is not already available on a session host, it is added during the logon process the same way it would be during a desktop logon. 

Wrapping up!

The ability to isolate app layers at the session level gives you an incredible amount of flexibility when dealing with one-off applications or if you are just looking to further consolidate images to reduce management time. The ability to dynamically attach applications at login, while still maintaining a native application experience in XenApp is not available anywhere else! Additionally, this feature allows organizations to support more applications (those one-offs and department apps come to mind) provide customized user experience that is generally only seen in VDI. But, now you can leverage your more scalable XenApp environment to support a number of VDI use cases,

If you would like to give Citrix App Layering a try, you can request a trial right from Citrix Cloud. Create a Citrix Cloud account (there’s no cost) and then select Citrix App Layering from the menu to access your 60-day free trial. The Citrix App Layering service includes full feature functionality and eligible customers with active Customer Success Services Select can use this service for production roll out.