Deleting the Sales Order Linked to Prodution Order

Hi all,

I have created Production Order with ref. to Sales Order and made the status Released.

Now my requirement is when i am able to delete the sales order which has been linked to the production order.I.e,At what status of production order the linked sales order will be able to get deleted.

For Eg.If the Status is settlement rule completed.them am i able to delete the Sales order.

And how do i know the status of production order that it is being processed or it is yet to get processed.

Thaks in advance,

M.Badrinarain.