Shared Data Tables

Hi TIBCO Community, Can someone explain what is the Shared Data Table (SDT) in Spotfire? What is SDT for the WP server, and what is this for Spotfire Server? What do we setup in Admin Manager via Preferences - AllowSharingOfCachedDataBetweenUsers?

When the report is cached in the WP memory,  what are the options avalable in WP? Can the user session object use the reference to single data table in memory for multiple users, or WP application will create new copy of the same data table per each session?