• From: "Dunbar, Norman (Capgemini)" <norman.dunbar.capgemini@xxxxxxxxxxxxxxxxxxxxxxxxx>
  • To: "smishra_97@xxxxxxxxx" <smishra_97@xxxxxxxxx>, "tim@xxxxxxxxx" <tim@xxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
  • Date: Fri, 14 Oct 2011 06:49:59 +0000

Morning Sanjay,

>> Can you please suggest as how the Top 5 Events suggest to go 
>> fortuning the topmost SQL in "SQL Ordered by Reads" 

The reason you need to look at the top few SQL statements "ordered by reads" is 
because your top 5 events are:

db file sequential read 32,512,212 200,101 8 69.58 User I/O 
DB CPU   40,112   11.30   
db file scattered read 2,123,189 29,289 13 10.51 User I/O 
db file parallel read 161,091 4,058 25 2.01 User I/O 
PX Nsq: PQ load info query 20,702 3,689 189 1.23 Other 

69.59% of your wait (Sorry Cary!) events are db file sequential reads. A 
further 10.51% are db file scattered reads and 2.01% are db file parallel reads.

"Reads" is the clue, your top 5 wait events are predominantly "reads". So, you 
look for the SQL doing the most reads and tune them. And don't forget, the best 
way to tune an SQL statement is not to execute it - so, don't retrieve data 
unless you have to.



Norman Dunbar
Contract Senior Oracle DBA
Capgemini Database Build Team
Internal : 7 28 2051
External : 0113 231 2051

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