Solution : https://service.sap.com/sap/support/notes/741776 (SAP Service marketplace login required)
Key words : 
symptom obsolete code page maintenance tools, cl_scp_segment_util=>read_codepage service method replaces, check reports return incomprehensible results, transport code page headers, code page maintenance transaction, obsolete scp_read_codepage module, basis release sap_basis 6, support packages belonging, sap code pages, obsolete links
Related Notes : 
       
| 548769 | BW Unicode Scenario: Dump CONVERSION_CODEPAGE_UNKNOWN |