So how did we go further? By using Oracle Enterprise Manager Grid Control (OEMGC), the queries which cause performance penalties, could be found quickly and so some extra indexes were made. But that wasn’t the only thing we saw during test. We also saw some queries running twice instead of running once. It happens for example by changing from one tab to another. Sometimes a query from the first tab was also run, before the second tab. For this behaviour we had to get support from EMC.
For other queries we need to check further, and came to the problem what Oracle has when FORCE is used for CURSOR_SHARING. The Oracle Optimizer doesn’t always like histograms with the setting of the parameter. After looking at the queries the histograms on the table DM_GROUP_R were the problem. So the statistics on the table were collected without the histogram and then these statistics were locked.