Very quick note on gathering of Exadata statistics.
Why?
Gathering Exadata specific system statistics ensure the optimizer is aware of Exadata scan speed.
Accurately accounting for the speed of scan operations will ensure the optimizer chooses an optimal execution plan in a Exadata environment.
Following command gathers Exadata specific system statistics
SQL>exec dbms_stats.gather_system_stats(‘EXADATA’);
Risk:
Lack of Exadata specific stats can lead to less performance optimizer plans.
Action / Repair:
To see if Exadata specific optimizer stats have been gathered, run the following query on a system with at least 11.2.0.2 BP18 or 11.2.0.2 BP8 Oracle software.