You attempted to open a database that is already opened exclusively by user <name> on machine <name>. Try again when the database is available. (Error 3356)

Possible causes:

You attempted to open a database that is already opened exclusively by the specified user <name>. You cannot open the database until the other user closes it.
You attempted to open exclusively a database that is already open in shared (non-exclusive) mode by the specified user <name>. You can open the database only in shared mode until the other user closes it.