The data warehouse is a relational database organized in a star schema with an OLAP database derived from that database. The OLAP database allows the reporting tools to access the derived information without degrading the performance of the relational database that actually stores the real-time information from the clients.
The warehouse stores several types of facts contributed by each of the Team Foundation tools as a primary relational table and a cube in the OLAP database that draws from that table. Each fact within a table has details, dimensions, and measures.
- Details Details are columns that appear in the primary fact table in the relational database and not in the OLAP cube. For example, work item titles are longer text strings primarily used in list reports.
- Dimensions Dimensions are the properties used to slice the data in a report. For example, dimensions of a Work Item fact include Type and State. Dimensions appear in the relational database as tables with foreign key references to the dimension tables from the primary fact table. All the facts have a project dimension that can be used to slice the data in the warehouse by team project.
- Measures Measures are properties that are aggregated, that is counted, added, and so on, to provide quantitative values in reports. For example, the CodeChurn cube provided by the source control tool includes LinesAdded, LinesRemoved, and LinesChanged measures. Measures appear as columns in the primary fact table.
For changes that are made to the process template, updates occur on each data load. By default, the data warehouse is updated once per hour. You can control how frequently the OLAP database updates the derived information it provides to the reporting tools. The schedule depends on the needs of your system.