How to get more accurate messages in P3401



Can someone please explain or provide a resource that outlines what fields have an effect on MRP messages showing in P3401? Right now there are far too many action messages being generated and we never act on them. They simply get deleted and and order gets placed for the correct quantity at the correct lead time. We never cancel, increase, decrease, change dates, etc. on existing purchase orders. So messages other than B, O, E, and G get disregarded right off the bat. We then leave one B or O message and check supply and demand to both determine quantity and promise/requested dates.

In addition to this, is there a way to have the message generate with the understanding that all orders from Supplier X will arrive on Wednesdays. So if lead time is set to 5 days but you have an O message created on Monday it knows that it should suggest the date of the following Wednesday (7 days out) rather than the following Monday (5 days out)?

Again, any resources or suggestions would be very much appreciated. I am assuming that there are quite a few fields that we do not have properly filled out on the part or supplier level but I have to clue what is critical to getting useful and accurate messages to generate.