In P6, you can define the date range for the Extended Schema. The range begins with the implementation date and a determined date range (for example, 3 years). Extending the range too far into the future will create large spread ranges. If you use the default range of 3 years, P6 will create a rolling window. As the services run, the window will continue to move. For example, January 1, 2012 and January 1, 2015 will become January 2, 2012 and January 2, 2015. If you have projects that last for three years, the projects will naturally fall in line and give you the spread data for this time frame.
Spread data represents a row in the database for each activity that has work on that day and for every activity in every project that is published. For example, if you have a project that has data reaching out 10 years and has 100 activities, you will have a spread row for 100 activities x 365 days per year x 10 years. Using this formula, data can add up quickly. The Extended Schema handles this and the ETL process quickly moves this data.
If you do not need these projects in Primavera Data Warehouse for analytical reporting, you can still use them in the Extended Schema for reporting. You can use a filter to decide which projects to include in the ETL process. By default, all projects with the Enable Publication setting in the Extended Schema will transfer to Primavera Data Warehouse.