Since multiple RDP sessions are disabled by default on Windows Servers, multiple concurrent remote sessions can be enabled by editing the Registry.
Because in Windows 2008/2012 RDP sessions are limited to two with one logon for one user, this setting may be useful in organizations who work with multiple administrators in the team to perform maintenance tasks.
When you try to RDP connect the server while another user is already connected, you receive the message:
In Windows Server (2008, 2008 R2, 2012, 2012 R2) open the Registry Editor and navigate to the following key:
Right click the fSingleSessionPerUser REG_DWORD and select Modify option.
Set the value from 1 to 0 then click OK.
The fSingleSessionPerUser key is now properly set.
Now you can establish multiple concurrent RDP connections to the server.