Revision History for Workbooks
9.3 Server can be set to keep a history of all published versions of a workbook. There is no revision history of data sources yet; hopefully that will come in future releases. You have to turn this on at the Site Level:
and then after that, you access from the Workbooks view:
Publishing a data source from a workbook automatically connects the workbook to the Published Data Source on Tableau Server
Previously, you had to manually connect to the new source in Tableau Server, do Replace Data Source, and then close out the original. In 9.3, there is a default option for this process to happen automatically.