2928975 - Field PURCHASEORDERQUANTITYUNIT error with PO API

You are creating a Purchase Order via API_PURCHASEORDER_PROCESS_SRV. The posting fails with error message:
'The input of field PURCHASEORDERQUANTITYUNIT on A_PurchaseOrderItemType level cannot be processed ( MMPUR_POHANDLER_TECH/010 ) linked to warning ME898

SAP S/4HANA Cloud Public Edition All versions

Execute a POST operation via API_PURCHASEORDER_PROCESS_SRV 
In the payload transfer a 'Purchasing Ordering Unit' via field 'PURCHASEORDERQUANTITYUNIT' that differs from the 'Base Unit of measure' defined in the material master
The system raised warning message ME898 and the posting fails with error MMPUR_POHANDLER_TECH/010

Missing master data

To be able to pass in a 'Purchasing Order Unit' different from the 'Base unit of measure' you need to activate the variable order unit in the material master (field MARA-VABME in TAB Purchasing) or if the combination has a Purchasing Info record you have to maintain the  'Var. OUn' ( field EINE-VABME )  in change 'Purchasing info record' under the general data TAB.

There is a specific system logic for the handling of alternate Ordering Purchasing Units of measure, for example when a reference document is used.
Attached is the detailed SAP Help found for message the ME898, this covers the different cases in detail, when creating a PO in dialog or via the API. (See Attachment for more details)

API_PURCHASEORDER_PROCESS_SRV, MMPUR_POHANDLER_TECH010, PURCHASEORDERQUANTITYUNIT, VABME, ME898, LMEPOF6D, ME_PROOF_VARIABLE_ORDERUNIT , KBA , MM-PUR-PO , Purchase Orders , Problem

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