The Active Sessions list contains the sessions (connections to debug
  servers) that this client has already established.  The session at the
  top of the list is the currently active session.  All debugger views
  reflect the context of the program being debugged on the currently
  active session.

  You can switch between active sessions by selecting a session from the
  Active Sessions list.  The Source view for that session is activated
  and all other debugger views are updated to reflect the program context
  of that session.

  All buttons on the Server Connection dialog, including Disconnect, Stop
  Server, Test and Properties as well as the status section of the Server
  Connection dialog are related to and act upon the currently active
  session.