Please can you tell me what are the impliations if the Internal order field status is changed from Optional to Mandatory.
Is this going to affect the any other areas of the system.
I understand you are refering to Internal Order field status in Order type. (Transaction code - KOT2_OPA). If you change the status from optional to mandatory, while creation of new order with reference to this order type, you need to maintain the values against mandatory fields. Otherwise you will not be able to save/create the new order.