mandatory fields for mapping in ORDERS idoc.

Hi

I m working on File to idoc scenario for creation of sales order in ECC 6.0 , now I want to know what are the mandatory fields in ORDERS idoc which needs to be populated or else disbaled so that the sales order gets created properly in the ECC 6.0..

Pl let me know the method of finding mandatory field for mapping for any idoc and which fileds of idoc are to be disabled.

Pl help ..

ans will be rewarded .

thanks & rgds

mojib