When you want to run MRP, entry user exit key and put your MRP controller as user exit parameter 

To define the user exit key, goto SPRO -> MRP -> Planning -> 'User exit material selection - MRP'. 

Then, go to SAP enhancement (SMOD) = M61X000, and add this code :

CLEAR: NO_PLANNING, STOP_PLANNING. 
CASE USER_KEY. 

*----------------------------------------------------------------------* 
* select materials for one MRP controller (specified in user_par) 
*----------------------------------------------------------------------* 

WHEN 'XXX'.      *MRP user exit key define in spro 
 UXPAR = USER_PAR. 
 CONDENSE UXPAR. 
 WRITE UXPAR+0(3) TO DISPO. 

 IF DISPO IS INITIAL. 
   EXIT. 
 ENDIF. 

 IF MT61D-DISPO <> DISPO. 
  NO_PLANNING = 'X'. 
 ENDIF. 

ENDCASE. 
 

Definition: MRP controller 

In a manufacturing plant, a person will be identified and will be responsible for a group of materials.  Material that takes part in material requirements planning must be assigned to an MRP controller.

MRP will guarantee material availability and once you run MRP, it will be helpful in planning as to whether what quantity a component should be procured or what quantity should be produced in-house.  Through MRP, you can automate procurement proposals for purchase and production.

MRP Controller is assigned in material master MRP1 view. 

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