How to handle Purchase Orders and Sales Orders with Old Material Numbers?

We are successful the process of replacing astir 9000 Materials with New Material Codes (This is done to activate Automatic Batch Split Valuation). Old Material Numbers volition beryllium maintained in MARA-BISMT. Stock volition beryllium moved to caller worldly code. I person a fewer questions regarding this.

1. Should existing Purchase Orders and Sales Orders beryllium closed earlier I bash this activity? Or is determination a mode to usage the caller worldly codes to bash goods receipt for existing POs and deliveries for existing SOs?

2. How bash I grip income instrumentality of older income orders?