RE: RDA - Top SQL report

  • To: <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 1 Mar 2006 18:35:12 -0500

Hmm...interesting...I've never looked at this guess would
be that they are speculating that a disk read takes about 20 ms, so,
disk_reads/50 would give you seconds.  Same idea for buffer_gets.  If a
buffer get takes 2 ms, then buffer_gets/500 will yield seconds.

As to how accurate that conversion is, well, that depends on way too
much stuff to speculate on.....


Mark J. Bobak
Senior Oracle Architect
ProQuest Information & Learning

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-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Srikanth Kalluri
Sent: Wednesday, March 01, 2006 6:11 PM
To: Oracle-L Freelists
Subject: RDA - Top SQL report

The question is regarding (Remote Diagnostics Assistant; Metalink Note:
314422.1) Oracle Support provides to troubleshoot performance issues in
a database {RDA} and the calculation of the "Top SQL Report"
More specifically, I am curious how the following ratios are deemed
"Expected Respose Time (in Seconds)"
From v$sqlarea:
 { (disk_reads/executions)/50 }
 { (buffer_gets/executions)/500 }
Also, what is the significance of the numbers 50 and 500 respectively?
Queries used in the report:
 disk_reads / decode(executions,0,1, executions) / 50 from  v$sqlarea
where  disk_reads / decode(executions,0,1, executions) / 50 > 100 order
by executions desc;

 buffer_gets / decode(executions,0,1, executions) / 500 from  v$sqlarea
where  buffer_gets/ decode(executions,0,1, executions) / 500 > 100 order
by executions desc;


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