Since I can never remember, I looked up in the QlikView Server Documentation, chapter 7.2 where it describes Session "Calls" as "Number of QlikView calls during the session (bidirectional)".
I honestly don't know exactly what that entails, but the intent of that metric is to provide more of an idea of the load on a server.
A session is when the user opens the app, but during that session, there are lots of 'calls' going back and forth.
Here's what I found from Qlik Support last year:
it’s a counter which counts number of requests that Server received during last performance collect interval.
- - Interval:
- Frequency for Server to collect the performance stats. By default, it’s 5 mins, and that’s the interval of “Timestamp” field in Performance.log;
- - Requests:
- All requests are sent through port 4747 to Server
- They mainly come from WebServer and QMC, sometimes from Plug-in or Desktop
- - Counter:
- It’s reset to 0 every time when we write stats down to Performance.log;
- It does NOT count
- those Authentication/Logon related ones.
- It does count:
- Normal requests from user web browser; (You can see them in browser’s developer console or Fiddler alike tools.)
- Control requests from QMC or WebServer; (Settings from QMC, load balance check, heart beat check etc..)
- Others directly from plug-in, desktop etc.
- - Interval: