Category-level SKUs
You can create SKUs under a category that are not associated with any product. This type of SKU is created for products that do not have defining attributes. For example, if you are selling a DVD, you do not need the association to a product in the same way you might with a man's dress shirt.
You can use category-level SKUs in stores that use non-ATP inventory, or no inventory. Category-level SKUs are not supported in ATP stores.
The following image describes the differences between category-level SKUs and product-level SKUs.
Note: If a SKU is not assigned to a parent product or a parent category,
the SKU will appear under the Unassigned Catalog Entries folder
in the Management Center explorer tree. By default, all SKUs that
appear in the Unassigned Catalog Entries folder
are product-level SKUs. When creating a category-level SKU in the
Management Center or loading a category-level SKU, you must specify
the parent category. Unassigned SKUs cannot be changed to category-level
SKUs.