How does "SQL Memory" in Spotlight home page is calculated, what does it represents?
SQL Memory values come from SQL Server’s performance counters. They are not about memory for the entire system but show how much memory the monitored SQL Server
actually and currently uses.
The “Total” value in SQL Memory in Spotlight home page comes from one of the counters for the SQL Server memory manager object named “Total Server Memory (KB)”.
Here’s the details of the SQL Server Memory Manager Object
To obtain the value in KB:
select counter_name, cntr_value from sys.dm_os_performance_counters
where lower(counter_name) = ‘total server memory (kb)’
Then cntr_value in KB will be divided by 1024 * 1024 to convert to GB.