As always with performance there can be many reasons why something got slower
and it’s hard to tell without further details.
However, have you made sure that you have set the system statistics to
Gather system statistics in Exadata mode if needed
Priority Added Machine Type OS Type Exadata Version Oracle Version
n/a Auguest 2012 X2-2(4170), X2-2, X2-8, X3-2, X3-8, X4-2 Linux
11.2.x + 126.96.36.199 BP18 and 188.8.131.52 BP8
Benefit / Impact
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. The following command gathers Exadata specific system statistics
Note this best practice is not a general recommendation to gather system
statistics in Exadata mode for all Exadata environments. For existing customers
who have acceptable performance with their current execution plans, do not
gather system statistics in Exadata mode. For existing customers whose
estimates are accurate, but suffer from the optimizer over estimating the cost
of a full table scan where the full scan performs better, then gather system
statistics in Exadata mode. For new applications where the impact can be
assessed from the beginning, and dealt with easily if there is a problem,
gather system statistics in Exadata mode.
Found in, and you may want to review: Oracle Sun Database Machine
Setup/Configuration Best Practices (Doc ID 1274318.1)
Gerald Venzl | Senior Principal Product Manager
Email: gerald.venzl@xxxxxxxxxx <mailto:gerald.venzl@xxxxxxxxxx> | Phone:
Oracle ST & Database Development
400 Oracle Parkway | Redwood Shores | 94065 | USA
On Jul 12, 2017, at 19:20, dedba@xxxxxxxxxx wrote:
I've migrated a datawarehouse to my new exa and now ran io_calibrate on it.
To my horror it returns worse figures than i expect, eg 500mb per second
throughput. The old & tired ODA clocks in at 3 times that, and more.. We do
see good performance on real queries, so the calibration is cearly wrong..
Any one has any pointers? Should I use auto-dop at all on an exadata?
Sent from my Android device with K-9 Mail. Please excuse my brevity.