We are trying to upgrade SAP BW from 7.3 to BW 7.5; before this, we've updated Oracle DB from 11.2 no unicode to Oracle 19c Unicode, then we've tested the system and it has very poor performance.
If we execute queries in old DB (Oracle 11.2 and BW 7.3) it have better performance than when we execute the same query with Oracle 19c and SAP BW 7.3
Oracle optimizer 11.2 it works better tha Oracle optimizer 19c.
After this ,we've upgraded to SAP BW 7.5 but we have same problem: SAP BW 7.3 Oracle DB 12 has better performance (executing query and data loads) than SAP BW 7.5 Oracle DB 19c.
We have to updated DB to 19c verion because of maintenance.
Do you know if there is any problem with BW 7.5 and Database Oracle 19c?.