Databases in SQL Server have three user access options:

* MULTI_USER - All users that have the appropriate permissions to connect to the database are allowed. This is the default.

* SINGLE_USER - One user at a time is allowed to connect to the database. All other user connections are broken.

* RESTRICTED_USER - Only members of the db_owner fixed database role and dbcreator and sysadmin fixed server roles are allowed to connect to the database, but it does not limit their number.

You can use the "ALTER DATABASE" to change database user access options as shown in the tutorial below:

USE GlobalGuideLineDatabase

GO

ALTER DATABASE GlobalGuideLineDatabase SET SINGLE_USER

GO

Now connect to server with another client session and try:

USE GlobalGuideLineDatabase

GO

Msg 924, Level 14, State 1, Line 1

Database 'GlobalGuideLineDatabase' is already open and can only

have one user at a time.

Go back to the first session and re-set the database to MULTI_USER:

ALTER DATABASE GlobalGuideLineDatabase SET MULTI_USER

GO