Solution : https://service.sap.com/sap/support/notes/1057511 (SAP Service marketplace login required)
Key words : 
terms oracle optimizer statistics cbo reason, automated statistics collection- check daily, experienced oracle/sap customers, oracle/sap world, -bi/bw environments, strong database knowledge, negative side effects, check sap note #588668, symptom alternative approach, negative plan change
Related Notes : 
       
| 588668 | FAQ: Database statistics |