To Update Quantity in Existing SAP Sales Order Document via IDOC Type ORDCHG

Hi All,

I have a request to update the order quantity of an existing SAP sales order number that will be sent from the third party to SAP. I am using IDOC Type ORDCHG with process code ORDC for changes to sales order. But, the result of the testing is a new line item is always created. I have read that I will need to maintain the POSEX field but I do not use that field and the third party will be giving us the same line item number as what in in the SAP sales order itself only. Thus, how do I get the IDOC to work to update the order quantity of an existing sales order document.

Appreicate all of your inputs.

Thank you!