Append Structure Missing in BSIS & BSAS in S4HANA

Dear All,

Presently I am working in a S4HANA 1809 conversion project. We are facing some issue related to BSIS and BSAS table. We have created two append structure in BSIS and BSAS in our ECC system. But in S4HANA BSIS is now defined as a DDL view and we are not able to find those append structure into that ddl source of BSIS and BSAS. Please suggest how to get back those field in S4HANA converted system.