Single-user mode can be set for the entire SQL Server or for individual databases using the Enterprise Manager. Once this mode has been set, only one connection to the SQL Server or specified database is allowed. Some administrative tasks can only be performed if single-user mode has been set.
Single-User Mode for the SQL Server
The SQL Server Properties dialog box opens.
The Startup Parameters box appears.
The new startup parameter is displayed in the Existing Parameters box.
Only one connection to the server is now possible.
When single user mode has been set, only one connection to the server is permitted. Therefore, keep the following in mind:
If the SQL Server Agent is running it occupies the only connection available to the server and you will be unable to establish a connection to the Enterprise Manager or Query Analyzer. Stop the agent to enable a connection to the Enterprise Manager.
If you are working with the Enterprise Manager and want to start the Query Analyzer, you first have to close the Enterprise Manager. Then start the Query Analyzer via the Windows Start menu.
Single-User Mode for a Database
The Properties dialog box appears.
Once single user-mode has been set, only one connection to the database is permitted. Each utility, including the Enterprise Manager, Query Analyzer and isql opens a separate connection to the server.