https://userapps.support.sap.com/sap/support/knowledge/en/2050848
2050848 - sp_downgrade to 15.0 from 15.7 fails with error 19985 - SAP ASE | SAP Knowledge Base...
Downgrading ASE 15.7 SP1xx to 15.0.3 Running sp_downgrade fails with error 19985: sp_downgrade 'prepare', @toversion='1503' go .... Checking datatypes in...