Friday, October 12, 2012

How To View Exadata Cell Offload On Enterprise Manager Grid Control

Sometimes we would like to review a SQL performance gain on Exadata. There are many ways to compare, here I would point out a view on Enterprise Manager Grid Control.

Login Enterprise Manager Grid Control --> find your DB --> click performance tab
-->click SQL monitoring -->click SQL ID you are interested in

If your DB is running on Exadata, you will see "Cell Offload Efficiency" on up right.
Move your mouse on the percentage number, you will numbers of "Bytes from disk"  "Bytes returned by Exadata"

"Bytes from disk" means how much bytes DB is expecting from Disk no matter exadata or not
"Bytes returned by Exadata" means Exadata Cells return how much data to DB on interconnect layer
By smart scan,filter,projection, Cell would return a subset data thus offload much traffic to DB layer.

Keep it in mind, sometimes the metric can be negative because of EHCC, ASM mirror...etc
Don't be surprise if you see something like -32%

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