Linking Accounting Documents to Source Documents 
Linking Accounting Documents to Source Documents
Use
An accounting document can be linked to a source document such as a billing document. If the accounting document is itself the source document of the business transaction, then no such link exists.
You can use the DRB to determine the links from the accounting document to the dependent source document.
Prerequisites
So that links can be defined for archived accounting documents you must create an information structure for field catalog SAP_FI_DOC_
001 or SAP_FI_DOC_002.
You are advised always to include fields AWKEY, AWTYP and AWSYS, otherwise these fields have to be determined direct from the archive, which you may find entails a long runtime.
As an alternative, the DRB also defines the links using the application-specific archive index (table ARIX_BKPF).
The link to the source document does not depend on whether the source document is in the archive or still in the database. What matters is whether the accounting document is archived.
If, for example, billing documents have been archived but not accounting documents then the link from the accounting document to the billing document (if this is the source document) still functions even if no information structure for the archiving object SD_VBRK is active.