planned order created even if there's an existing production order
sales order due date is 21.10.2008. a planned order was created after mrp run, and it was converted into a production order. the dates of the production order was adjusted to start and finish 24.10.2008. however, after an MRP run, a new planned order was created for the sales order. so now there are two orders ( 1 planned, 1 production ) for one sales order requirement. why is this happening?
As you have explained, you have changed the finish date of the production order to be 24th October which is after the 21st October due date of sales order. Hence when MRP is run, it sees that the sales requirement cannot be meet by the production order and hence it creates a new planned order to meet the requirement for 21st October.
Please let us know is there any specific reason why you changed the production order finish date? Ideally you are not supposed to change the production order finish date if it is connected to a sales order.
Hope this helps.