Solution : https://service.sap.com/sap/support/notes/425593 (SAP Service marketplace login required)
Key words : 
db4_auto_inzpfm rsadmin parameter controls, sap bw support packages, bw support packages, support packages provide, activate automatic initalization, deactivate automatic initialzation, full table scan, 0b support package 27, 1 content support package 21, existing access plan
Related Notes : 
       
| 567745 | Composite note BW 3.x performance: DB-specific setting | 
| 339885 | AS/400: Performance when fetching fact tables | 
| 63037 | AS/400: Deleting SQL Packages |