You should monitor the performance of the Px services. While the database size plays a role, the volume of changes made will affect performance most. Even a small user community can generate a large amount of changes with functions like copy/paste, delete project, and create baseline, as well as simple changes to global resources like calendars. You should monitor the amount of changes made prior to installing the products to better plan the implementation.
Primavera Data Warehouse always runs a full ETL process. Fresh data is pulled from the P6 EPPM schema and existing history table data are preserved during the ETL process. You must decide whether to implement a history data purge process.