Solution : https://service.sap.com/sap/support/notes/33814 (SAP Service marketplace login required)
Summary : 
      
Key words : 
dbthe oracle tool brconnect issues warnings, unique indexobligatory base oject missing, br970w database administration alert - level, missing dbdiff entries occur sporadically, symptom transaction db02 reports, terms indexes reason, informix based systems, additional customer entries, bw support packages, avoid in_wrong_tablespace warnings
Related Notes : 
       
| 849692 | Temporary SCI_TEMPT table | 
| 790292 | Filestat table raises warnings in DB02 or brconnect | 
| 664034 | DB6: DB02 displays missing indexes in APO | 
| 644479 | BRCONNECT messages concerning STATS$ tables | 
| 579493 | DB6: SAP_UPDATE_DBDIFF adds P indexes into the DBDIFF table | 
| 526774 | Informix: SAPDBA Tables and DDIC Unknown Objects | 
| 503505 | DB6: Inconsistent entries in transaction DB02 | 
| 497135 | DB6: Incorrect source entries in the DBDIFF table | 
| 449891 | Temporary database objects in BW 3.x | 
| 446045 | STM$BH table displayed as 'missing table' in DDIC | 
| 319002 | AS/400: DB02 reports an inconsistency for system catalog vie | 
| 308533 | Temporary Database Objects in BW 2.0 | 
| 193201 | Views PEUxxxxx and TEUxxxxx unknown in DDIC | 
| 127037 | Addit.info on upgrade 3.0F+EURO-CNV 3.0F -> 4.0B | 
| 117219 | DB02 reports missing DD/DB objects: procedure | 
| 109083 | Maintenance of tables in SE16 not allowed |