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RE: Why wait?

From: Mark Leith <mark_at_cool-tools.co.uk>
Date: Wed, 24 Apr 2002 05:53:26 -0800
Message-ID: <F001.0044DB06.20020424055326@fatcity.com>


I personally believe that monitoring the SQLArea for any poor performing SQL should also be done on a regular basis (*as well as monitoring the "OWI" (:P)*).. The end result should be to build as complete a picture as possible as to what is running through the system, where users are waiting, and the response times that they are getting.

By and large - 80% of performance problems seen with Oracle databases are caused by poorly performing SQL. With that in mind - my feeling is that this is one of the main areas that a DBA should be monitoring over a period of time, archiving any "offenders" (whether this be by DISK_READS, BUFFER_GETS, BUFFER_GETS/EXECUTIONS etc..) to a table or flat file or whatever "floats your boat", and return to that "archive" once in a while to see if they can make any improvement to the "dogs" that are hounding the system..

V$VIEWS are your friends.. Just because somebody recommends monitoring by wait events, doesn't mean you can't go on to monitor by some other criteria, and build a more comprehensive view of what's happening.

Just my 0.02 pence

Mark


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-----Original Message-----
Sent: 24 April 2002 13:59
To: Multiple recipients of list ORACLE-L

There's something I don't understand. Why use the wait interface to investigate "db file scattered read" or "db file sequential read"?

The end result is finding an SQL statement that does a lot of reads. There's no guarantee it's a poorly tuned SQL statement, just that it does a lot of reads.

If that's what you want, why not just query v$sql and order by physical reads? Doing this is a whole lot easier. Also, unlike the hit and miss results from v$session_wait, v$sql provides a comprehensive picture.

Thanks for your input. Cheers!

--

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Author: Mark Leith
  INET: mark_at_cool-tools.co.uk

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