How to identify current back orders or order lines



How to identify all the current back orders (F4201) or back ordered lines (F4211).

I understand that SDLTTR can be 900, 902, 904, 909 for back order lines. however i read that this status remains same even after order line is released. so is there a way to identify the current back orders?

Apart from the status, adding additional condition like SDSOBK != 0 is correct? or do i need additional conditions to determine all current back orders?

Any help is appreciated.