get away from Document Hash in File Adapter integration in AX 2012 ?

My understanding is that if RecId and RecVersion are there in the file then document hash is not needed (link ). But this is not working for me with documentHash provided in file it works fine, the moment I take out documentHash request fails with error:

"Field _DocumentHash must be filled in"

an FYI.. I have provided RecId and RecVersion in both the cases.

How can I get away from DocumentHash for just this service through File Adapter.

Also, where can I find the code that checks DocumentHash between DB and the request ?

Thanks in Advance,

San.