Solution : https://service.sap.com/sap/support/notes/449891 (SAP Service marketplace login required)
Key words : 
open hub read processes, terms business information warehouse, open hub function, bw open hub, process external hierarchies, run report sap_drop_tmptables, execute report sap_update_dbdiff, report copies information, bw system defines, system compresses/condenses
Related Notes : 
       
| 1165174 | Performance optimization for queries with hierarchies | 
| 1139396 | Temporary database objects in BW 7.X | 
| 1068324 | Views are not dropped after usage in hierarchy queries | 
| 1031929 | Deadlocks at concurrent deletes on the same hierarchy table | 
| 1013912 | FAQ: Oracle BW performance | 
| 974639 | SAP_DROP_TMPTABLES: Nametab is deleted incompletely | 
| 830468 | FAQ: Business Information Warehouse system with SAP MaxDB | 
| 755147 | SQL error -3007 when you access DB system tables | 
| 706478 | Preventing Basis tables from increasing considerably | 
| 648203 | Database objects with INVALID status | 
| 514907 | Processing complex queries (data mart, and so on) | 
| 308533 | Temporary Database Objects in BW 2.0 | 
| 33814 | Warnings of inconsistencies between database & R/3 DDIC |