Message SAP WRF_PRC_POHF218 - Processing of the group of vendor orders failed

Diagnosis
At least one error occurred during processing of a group of documentsfor the same collective number.

System Response
The system cannot create purchase orders for the entire group. Thesystem creates grouped purchase order documents (GPOD) for the data.
Technical note:
A ROLLBACK WORK will be performed for the current collective number. Ina second run, the GPODs will be created by the BAPI. If the only "error"is a shortage of OTB, this message represents the only indication of anerror, because OTB does not (currently) issue any error messages of itsown.