Before adding, removing, or moving a Controller, if your deployment uses database mirroring, ensure that the principal and mirrored databases are both running. In addition, if you are using scripts with SQL Server Management Studio, enable SQLCMD mode before executing the scripts. To verify mirroring after adding, removing, or moving a Controller, run the get-configdbconnection PowerShell cmdlet to ensure that the Failover Partner has been set in the connection string to the mirror.
Removing a Controller does not uninstall the Citrix software or any other component; it removes the Controller from the Database so that it can no longer be used to broker connections and perform other tasks. If you remove a Controller, you can later add it back to the same Site or to another Site. A Site requires at least one Controller, so you cannot remove the last one listed in Studio.
Do not remove the Controller from Active Directory until after you remove it from the XenDesktop Site.
After using Studio to remove a Controller, traffic to that Controller might linger for a short amount of time to ensure proper completion of current tasks. If you want to force the removal of a Controller in a very short time, Citrix recommends you shut down the server where it was installed, or remove that server from Active Directory. Then, restart the other Controllers on the Site to ensure no further communication with the removed Controller.