Availability check

Hi All,

When i do the cash sales,the availability check is performed and the dialog box of avilability control pops up.My Material type in MMR is PD.

My question is why the availability check is occuring as there is no link between the item category BVN and the material type PD in "Assignment of req type to transaction".

I mean which Tcode is initiating the availability check for the cash sales orders.

Please advice

Rishi