Received an email from Roy last night with some performance issues a customer in the US encountered recently during their upgrade testing.
One issue the customer encountered has to do with tons of parallel slaves creating a massive noise on the system when they are doing a CTAS (Create Table As Select) – and the same thing happens with an IAS (Insert Append Select).
What caused this change?
In this case the behavior change is well documented, even though not linked to the responsible underscore parameter.
- Oracle White Paper: Best Practices for Gathering Statistics –