Solution : https://service.sap.com/sap/support/notes/407528 (SAP Service marketplace login required)
Key words : 
optimizer estimates dynamic bitmap indexing, db2/400-based bw system release 2, -unique secondary index called /bic/, terms business information warehouse, db2/400-specific bitmap index, tabstrip control 'database' - 'indices, affected tables start /bi0/, dynamic bitmap indexing, 0b support package 18, bw support packages 2
Related Notes : 
       
| 503238 | iSeries: Yellow traffic light with index check | 
| 501572 | iSeries: EVI stage 2 support | 
| 451808 | iSeries: Adjusting indexes to the new index schema | 
| 442902 | iSeries: Corrections for BW 3.x | 
| 407530 | AS/400: BW 2.0B/2.1C on DB2/400: DBDIFF Handling | 
| 328322 | DB6: DB2 UDB EEE Indexing Scheme of BW Facttables | 
| 308537 | iSeries: Corrections for BW 2.0B / BW 2.1C | 
| 217397 | Indexing Scheme of BW facttables under Oracle | 
| 184905 | Collective note Performance BW 2.0 |