SQL Kill  connections on a database , sometimes is the most efficient way forward.I had to copy a whole bunch of MDF\LDF files from a server , but was experiencing some problems regarding user connections.

I was trying to detach using this code:

#####################code start#############################
USE [master]
GO
EXEC master.dbo.sp_detach_db 
@dbname = N'MY_DB', 
@keepfulltextindexfile=N'true'
GO
#####################code end#############################

which was not allowing me to detach . The following code allowed me to clear the connnections and
do the detaching

#####################code start#############################

alter database MY_DB set single_user with rollback immediate  

alter database MY_DB set multi_user with rollback immediate  
#####################code end#############################