You would need to monitor a session if the current request in that session is progressing very slowly and taking much longer than expected to complete. The session in that case needs to be investigated before the request may in turn use more resources (CPU, IO, Spool) than it should and possibly degrade the performance of other sessions on the system.
In these cases you would need to monitor and identify the session in order to get more information about the session. What is the session doing? Why is it behaving that way?
Viewpoint, SQLA, or other performance monitoring applications are used to establish common ground and improve the analysis if any of the tools. We might not have access to one tool and might use another to ...
