Users can publish workbooks to Tableau Server or Tableau Online, but extracts won’t refresh automatically unless a scheduled refresh is applied.
Scheduled Refresh automates data updates, so users don’t need to republish workbooks every time data changes. For example, you can schedule a refresh at 7 a.m. to ensure your ServiceNow reports are updated by 9 a.m.
With Tableau Connector for ServiceNow you can schedule refreshes to get the actual ServiceNow data.
It is impossible to stream live ServiceNow data to Tableau and have a real-time synchronization.
Based on the information from Tableau community, not all sources allow streaming live and real-time data in Tableau at the moment. Based on our customers' best practices, we kindly recommend using a scheduled refresh to get actual ServiceNow reports in Tableau.