Hi,
When an order (planned order / production order / process order) is intended to transfer to APO there can be some performance issues along with the error
Order type X order number XX Method
A table entry already exists with this secondary key
(/SAPAPO/OM_ERROR215)
Kindly run report RGUIDDEL in ECC system in order make the table CIFORDMAP consistent since this table has the entry for R/3 order number along with APO GUID. But please make sure that this report is initially run in test mode in order to check as in which tables will be deleted once this report is run, generally the tables CIFPOMAP, CIFSLSMAP AND CIFORDMAP will be deleted, hence run it in test mode and then to the main mode.
Also make sure that note 1831837 is implemented in your system
Thanks
Gomathi