Each product can have multiple parent categories, one for each catalog that includes the product. Therefore, you must designate a reporting catalog, which determines which catalog supplies the parent category information for a given product. You can do this in the reportingCatalogId property of the /atg/reporting/datawarehouse/CommerceWarehouseConfiguration component. This property is null by default. If the property is null and a product has only a single parent category, that category is used. If it is null and there is more than one potential parent category, the first category is used, and a warning is logged.