Hi David, I think the real problem was a series of bad decisions :D I also think that Query Rewrite is not bad at all. The behavior was unexpected and should be checked before implementing MViews with such an option. But I think this is applies for any technical solution.

Hi Philipp, thank you very much for your response :) I've added a note for the long parse time. The queries were using many objects via Views on Views on Views with the MViews in between. So we used a lot of objects (can't remember the exact number anymore) and the parse time seemed to be reasonable. At least the Tuning guys didn't mention it specifically :D What bothers me is the different behavior when selecting data from a query with Query Rewrite and selecting data from the Materialized View directly. I can imagine that the Optimizer is forced to get a new plan due to changes in the data. Maybe it would then decide to query the data directly from the table and not from the Materialized View 🤔