MRP element Tr.res in MD04

Hi All,

We have 2 plant 9000 and 9001 , both plants are under same company code 1000. We have one material X001 , which is extended in both the plants. We have maintained Source list and purchase info record of this material. In Source list we have maintained 88888 as fixed vendor.

We have demand for material X001 from sales order . Now when I run MRP for material X001 and plant 9001. Then Planned order getting generated.

But When I saw MD04 of material X001 and plant 9000. It generates Tr.Res in MRP element.

So, will you please explain in which cases system shows status of MRP element in MD04 as Tr.res  ???