Issue in populatng the Message Function Field in control records.

Hi , mine is a scenerio , whn I am sending unformation from MDM to PI to ERP system . ERP is getting updated with MDM information by idoc(ADRMAS). Now , in the inbound idocs in ERP , the control record field needs to be populated with a field called Message Function . This field is also vsisble in partner profile - inbound/outbound parameters - next to message tpye field - message variant field .

I wish to know , where and how is this field is populated. As based on the value of this field , the information from inbound idoc is going to be treated as craete/ modify etc in the data base tables. Is it in the distribution model?? Please suggest !!

Arnab