I think putting in foreign key constraints will slow down the DML's. In case of staging tables where data is inserted and deleted intensively the strategy of putting in constraints may not be useful. We had a situation like this recently where the performance of a screen used for uploading records into the staging table through webutil performed badly since the foreign keys were put with the actual base tables. In this case it's better to leave the task of validations to the batch processes rather than freezing up the screen for long. Please let me know your views.