Run the following T-SQL script for listing all active sessions in all SQL Server databases of the open SQL instance.
SELECT DB_NAME(dbid) AS DBName, COUNT(dbid) AS NumberOfConnections, loginame FROM sys.sysprocesses GROUP BY dbid, loginame ORDER BY DB_NAME(dbid)
This will return a list of the active sessions, grouped by the number of active connections and login name and ordered by the name of the database.
Alternatively you can run the sp_who stored procedure by executing the following command as a script inside SQL Server Management Studio:
Also you can open the Activity Monitor tool by right clicking on the SQL instance inside the SQL Server Management Studio and choose to launch the Activity Monitor. This shows a list of parameters of the active SQL instance and databases, such as running processes and system resources consumed.