Data Sources for Team Foundation Server Reporting
Team Foundation Server reporting uses two data sources, TfsReportDS and TfsOlapReportDS, for its pre-built reports. Both data sources can be viewed in Report Manager on the team project report site.
TfsReportDS points to the relational database TFSWarehouse using the connection type "Microsoft SQL Server." The reports delivered in the MSF process templates use the TfsReportDS connection to retrieve the last warehouse update that appears at the top of the report.
TfsOlapReportDS points to the Team System data cube in the analysis services database TFSWarehouse using the connection type "Microsoft SQL Server Analysis Services". All the pre-built reports use the TfsOlapReportDS data source to populate the report.
Because the data cube is designed to improve the efficiency of analyzing and reporting data, you should build your custom reports using the TfsOlapReportDS data source.