To identify the top Sessions consuming high resource, Click "Top Session" button.
By default, it will fetch the latest 15 minutes top sessions in your database, you can change the time slot to get the history top sessions. The top sessions are sorted by waits by default, you can also get the top Sessions list sorted by CPU, IO, PGA or Temporary Space.
When you choose the top Sessions sorted by PGA or Temp Space, it will give you the maximum PGA/Temp Space of these sessions consumed.
Choose one of the top sessions, then click "Session History", you will get the history details of the selected session. Further information of session History, please refert to "Show Session List".