Changing Sales Order Items Relevant for Rules-Based ATP Check 
It may be necessary to change sales order items that are relevant for rules-based availability check (rules-based ATP check, or RBA). The following situations may apply:
A customer may want to change the requested delivery date or the product quantity. In this case, you can change the sales order items manually in SAP CRM.
The supply situation may change significantly, so that it is necessary to carry out a new rescheduling run (using backorder processing) in SAP Advanced Planning and Optimization (SAP APO). In this case the changes are transferred back to the sales order items in SAP CRM..
You can change the following:
The customer's request, that is, the main item
The results of the rules-based availability check, that is, the subitems
Availability check is then carried out for the open quantity.
Automatic determination of the location takes place when rules-based availability check is carried out for the first time. For subsequent availability checks, SAP CRM transfers the location to SAP APO.
Note
You can also carry out availability check manually for an item by selecting the item and choosing .
If none of the subitems has been delivered or canceled, you can change the following:
Product
Requested Delivery Date
Quantity (denotes the requested quantity)
You can also delete schedule lines for the main item.
After you have changed the main item, rules-based availability check is carried out for the main item.
In this case, SAP CRM does the following:
Delete the corresponding subitems if they have not been replicated to the backend system
Cancel the corresponding subitems if they have been replicated to the backend system. In this case, the confirmed quantities are released so that they are considered as available during the new availability check.
Change the item category of the main item back to the original item category
Create new subitems if the requested product or location is substituted. Otherwise, the main item is confirmed.
If an RBA subitem has not been delivered, you can change its requested quantity. The requested quantity is adjusted automatically in the main item. Availability check (not rules-based) is carried out automatically for the subitem.
You cannot change the following:
Product
Requested Delivery Date
Note
If you change the main item and one or more of its subitems, the changes to the main item take priority. That is, the changes to the subitems are ignored, and rules-based availability check is carried out again automatically for the main item.
Certain restrictions apply when you change sales order items which are relevant for rules-based availability check:
You cannot change the item category in the main item.
You cannot delete the main item.
Note
We strongly recommend that you do not delete the subitem.
You cannot create new request schedule lines for the main item.
If you need to carry out availability check for a sales item after rules-based availability check has already taken place, you select the item and choose . The system then carries out availability check for the subitems without rules. That is, availability check is carried out in the location determined during the previous availability check.