Sessions in Vertica

Hi,

I recently started using community edition of vertica and even after going through the documentation, I have following questions on SESSIONS in vertica:

1) What is the concept behind session in Vertica? My understanding as of now is as follows: Every login gets one session. For example, if 5 users are using the same login to access Vertica (assuming all 5 of them have 1 SPID each), then there will be 5 sessions in the sessions table. Is my understanding correct? If NO, could you please explain it over here?

2) Does Vertica close the session automatically once the job executes? For example, I have a cronjob set up which runs daily, and creates few tables on vertica and ends. So would it close the session automatically which it created on vertica? If Yes, I dont see this behaviour on Vertica as of now. I have to manually close these sessions once the Maxclientconnections has reached. Please advise what should be my approach here. I dont want to pile up my sessions table.

3) Also, while closing sessions, I see lot of system queries in the sessions table. I would like to know more about these. Can we safely close these sessions?

Also, please point me to the documentation which has the concept of sessions explained in detail.