RE: I/O waits hurting anyone?

From: McPeak, Matt <>
Date: Tue, 18 Feb 2014 17:47:18 +0000
Message-ID: <>

Yes.. maybe I didn't ask the right question.

The reason this came up was because the DBAs had a report generated showing this SQL as the #1 in the database over the past week. But it's only #1 in terms of elapsed time.

When I look at these things, I usually look for actual work: gets, physical reads/writes, cpu time, etc and ignore elapsed time.

The rationale being: if it is not doing a physical read/write and it is not using CPU, who cares?

So I am wondering if there is something else about "elapsed time" that makes it a good metric for identifying tuning targets.


From: Mark W. Farnham [] Sent: Tuesday, February 18, 2014 12:31 PM To: McPeak, Matt; 'ORACLE-L'
Subject: RE: I/O waits hurting anyone?

That depends largely on two factors:

  1. How much of your i/o "wait" is actually cpu/data movement, burning cpu.
  2. Whether your i/o is obstructing some other job's need for data access


From:<> [] On Behalf Of McPeak, Matt Sent: Tuesday, February 18, 2014 12:24 PM To: ORACLE-L
Subject: I/O waits hurting anyone?

I have a process that executes a lot. Over 6 days it's executed 1.3 million times. The elapsed time per call averages 0.8 seconds, and the I/O wait time per call averages 0.7 seconds.

In other words, it spends most of its time waiting.

I'll look into all that... my question is more general: am I right in saying that the I/O waits don't load the system in any way and don't hurt any processes besides the one that is waiting?

Thanks in advance!


Received on Tue Feb 18 2014 - 18:47:18 CET

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