RE: I/O waits hurting anyone?
Date: Tue, 18 Feb 2014 17:47:18 +0000
Message-ID: <D7864FA3E7830B428CB2A5A5301B63EE7D2A3A06_at_S7041VA005.soa.soaad.com>
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.
Thanks,
Matt
From: Mark W. Farnham [mailto:mwf_at_rsiz.com]
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:
- How much of your i/o "wait" is actually cpu/data movement, burning cpu.
- Whether your i/o is obstructing some other job's need for data access
mwf
From: oracle-l-bounce_at_freelists.org<mailto:oracle-l-bounce_at_freelists.org> [mailto:oracle-l-bounce_at_freelists.org] 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!
Matt
-- http://www.freelists.org/webpage/oracle-lReceived on Tue Feb 18 2014 - 18:47:18 CET