APEX

apex.server.process(
 "GET_ITEMS_JSON",
 { pageItems: "#P42_MPI_ID" },
 {
   dataType: "json",
   success: function (data) {
     if (data && data.length && data[0].error) {
       apex.message.alert(data[0].error);
       return;
     }
     var region = apex.region("DWM_INFO");
     var widget = region.widget();
     var grid = widget.interactiveGrid("getViews", "grid");
     var model = grid.model;
     data.forEach(function (r) {
       console.log(r);
       var recId = model.insertNewRecord();
       var rec = model.getRecord(recId);
       
       model.setValue(rec, "ITEM_ID", r.ITEM_ID);
       // model.setValue(rec, "ITEM_UNIT", r.ITEM_UNIT);
       // model.setValue(rec, "QUANTITY", r.QUANTITY);
     });
   },
   error: function (xhr, status, err) {
     apex.message.alert("Load failed: " + err);
   }
 }
);

why after setting the value and save, all I see in the database is null values?