Solution : https://service.sap.com/sap/support/notes/1427864 (SAP Service marketplace login required)
Key words : 
luw condenser merge real time statistics failure due, statistic collection appears due, enabled real time statistics, setting rsadmin parameter db6_rts_runtime, set rsadmin parameter db6_rts_runtime, real time statistics, rsadmin parameter db6_rts_runtime, default time interval, prerequisites performance problemsduring, log file resides
Related Notes : 
       
| 1412879 | DB6: SAP BW Compression Performance Problems | 
| 1397029 | DB6: Improvements and code fixes in RSADMIN parameters | 
| 1342193 | DB6: Changes for DB2 9.7 | 
| 1087783 | DB6: Code Changes for Real Time Statistics DB2 9.5 | 
| 593118 | DB6: Runstats during compression, RSADMIN parameter |