Could not connect. The maximum number of '%1!ld!' configured user connections are already connected. The system administrator can change the maximum to a higher value using sp_configure.
This error results when all configured user connections are in use and a request to create another Microsoft® SQL Server™ process occurs. SQL Server is not configured with enough user connections to support all requests. There is one process slot structure (PSS) for each configured user connection.
Use the sp_configure system procedure to increase the number of user connections:
sp_configure 'user connections', new_number
GO
RECONFIGURE
GO
Depending on the exact configuration of your SQL Server installation, each user connection requires 37 KB of memory, whether or not it is in use. Gradually increase the number of user connections until this error no longer occurs. When you change the user connections parameter, you may need to increase the memory parameter.
sp_configure | Setting Configuration Options |