A bank statement line item can be linked with up to two accounting documents.
You can use the DRB to determine the link from an archived bank statement line item to the accounting documents, or conversely the link from an accounting document to archived bank statement line items.
To determine the link, you need in both cases an archive information structure for field catalog SAP_FI_ELBANK_2.
To determine the link from an accounting document to archived bank statement line items, you need an archive information structure for field catalog SAP_FI_ELBANK_2 that also contains fields BELNR and NBBLN.
To obtain the best runtime, you are recommended to create two secondary indexes for this archive information structure as set out in SAP Note 164704. These should contain the fields MANDT and BELNR or MANDT and NBBLN.
To determine this link for line items you have not yet archived, you need corresponding database indexes in table FEBEP. These database indexes should begin with the fields MANDT and BELNR or MANDT and NBBLN.
In both cases it is immaterial whether the linked accounting documents have been archived or are still in the database.