UOM of PO Quantity cannot be changed

Question

Hi Experts,
I have a requirement to change the UOM (Unit of Measure) of the PO quantity. The UOM has to changed from EA to MON. When I try to do that in the DOC_CHANGE badi, the system reverts back the changes in the PO with a information 'Unit of measure cannot be changed'.
Can someone let me know how to change the UOM in PO through this BADI or by some other means.
Thanks & Regards,
SRS

Answer 1

Hi David,
I accept that the PO quantity unit cannot be changed after the SC is approved. But there is a specific requirement in my case where the unit of measure needs to be changed when the buyer processes the PO (after the SC is approved). The new UOM is a custom one in my case.
This cannot be done in SC method of BBP_DOC_CHANGE_BADI. The reason is due to the fact that the BADI implementation is not called in the approval process.
I found out a way, although it is not the right one.
Creating custom UOM
SRM & ECC
In the UOM customizing (Tcode CUNI), copy the original UOM of the PO and create a new custom unit of measure. Uncheck the 'Primary ISO code' indicator. Don't change the ISO code of the new UOM. Maintain the other parameters (Int. meas. unit, Commercial, technical, Measurement Unit text) according to your requirements.
BADI Implementation
1) Create a BADI implementation of BBP_DOC_CHANGE_BADI
2) In the method BBP_PO_CHANGE, with the help of PO guid (lt_item-guid), update BBP_PDIGP with the custom UOM
3) In the same implementation, with the help of SC guid (lt_item-src_guid), update BBP_PDIGP and PRCD_COND with the custom UOM
4) Call FM BBP_PD_PO_RESET_BUFFER.
Now the new UOM of measure is updated in the PO, SC when the PO is processed.
Thanks & Regards,
SRS