Attachment transfer from SRM to ECC

Dear all,

Working in SRM 7.02, Transfer the document using PI.

1. The SC that is created in SRM has attachment -> SOCO-> ECC PO. But the XML message doesn't have the attachment.

2. SC-> SOCO-> RFX-> RFx Reponse with Attachment-> ECC PO. Bu there is no attachment in XML message.

Normally the PI structure (PurchaseOrderERPRequest_Out_V1) has no attachment infromation.

then how the attachment needed to be transfer..

Kindly let me know the procedure to transfer the attachement..