Hi Nitesh, is this for Tableau Server?
As far as I know, once you meet the minimum system requirements there shouldn't be a problem if multiple users are logged in at the same time. Are you concerned about something in particular? (eg: speed of vizzes)
Link to tech specs / system requirements --> All Technical Specifications | Tableau Software
I've also added a link to general performance guidelines, with some tips that may be of use
Hope this helps