Prerequisites
The RDS instance runs SQL Server 2012 or later.
Procedure
You can close only the connections initiated by you and cannot close other connections, such as backup connections. You can run the following command to close a connection:
KILL <Process ID>
You can execute the following statement to query active sessions and processes:
SELECT session_id, login_name, status
FROM sys.dm_exec_sessions
WHERE is_user_process = 1