At times, we may need to take a database offline. And there is a chance that we encounter an error message like below.
How do we solve this issue and take the database offline?

Msg 5061, Level 16, State 1, Line 1
ALTER DATABASE failed because a lock could not be placed on database 'DBNAME'. Try again later.

Solution:
If there are any connections open, then there is a lock on the database while getting the database into Single user mode/taking offline.
To resolve the issue, as a first step you need to kill all the sessions on the database followed by the ALTER database statement.

USE master;

DECLARE @killSessions varchar(8000) = '';  
SELECT @killSessions = @killSessions + 'kill ' + CONVERT(varchar(5), spid) + ';'  
FROM master..sysprocesses  
WHERE dbid = db_id('dbname')
EXEC(@killSessions); 

ALTER DATABASE dbname SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
GO
ALTER DATABASE dbname SET OFFLINE WITH ROLLBACK IMMEDIATE
GO
ALTER DATABASE dbname  SET MULTI_USER;