Attach database failed for Server. (Microsoft.SqlServer.Smo) An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo) Unable to open the physical file . Operating system error 5: "5(Access is denied.)". (Microsoft SQL Server, Error: 5120)

Connect to the server using an administrator account with access to the file system for the database files and through Windows Authentication rather than using sa through SQL Server Authentication.

Taking a SQL server database offline fails or killing a database connection

In most cases, when the operation for taking a database offline; this is attributed to connections established to this database. The apparent solution is to close the locking connections, the below is how to force them closed.


Use [master]
GO

sp_WHO 
GO

spid | ecid | status   | loginame | hostname | blk      | dbname | cmd 
58    | 0     | sleeping| user1        | user1PC   | NULL| MyDB   |LOG WRITER      


KILL 58
GO

Command(s) completed successfully.





P.S. 
- sp_who2 provides even more details about the current connections.
- No need to mention that you must have the appropriate rights on the master database to perform this commands.