>>>>>Me again :)
>>>>>
>>>>>I have confirmed from the Citrix engineer that (as Dragan correctly wrote) each user of my application will have a separate memory space (hence each user will have a user ID and password). And I wrote to the Citrix engineer that my app needs a minimum of 2 GB of RAM (just a guess on my part :)).
>>>>>But now I am thinking. If 20 users log into the Citrix server to use my app and each is allocated 2 GB or RAM, would they (Citrix engineers) need to have the server with a minimum of 40 GB of RAM?
>>>>
>>>>I just recently had 3 users sharing a 2Gb server and it was awful. I pushed the ram to 8GB which worked much better.
>>>
>>>Is your server a Citrix server?
>>
>>RDP.
>
>Ok

A little while back I was managing a small collection of Hyper-V VMs. One of the VMs was Server 2012 R2 running solely as a primary domain controller. Its steady state RAM usage was 0.9 GB.

If you have a virtual or physical server with only 2GB RAM, that means you're trying to cram the Remote Desktop role (and maybe the RD Gateway role as well) plus 3 user sessions into 1GB RAM. That may over-allocate RAM, but even if it doesn't it would certainly leave very little available for disk cache, so the user sessions would likely be constantly paging to disk, which would be painfully slow if the disk subsystem is magnetic.

I think Mike might have misinterpreted what you were saying, and thought you're trying to run multiple Citrix sessions on a server with only 2GB total RAM, which would be painful. Your initial thought was 2GB per session, which is too high. You'll probably end up somewhere in the middle ;)