Re: Log File Syncs

From: Andrew Kerber <andrew.kerber_at_gmail.com>
Date: Thu, 24 Mar 2016 09:46:49 -0700
Message-Id: <DC924010-4EB2-4139-9757-4E257FAD74A2_at_gmail.com>

the obvious question is what is the underlying hardware? All you have told us is that we have a physical server and a virtual server.

Sent from my iPhone

> On Mar 24, 2016, at 8:58 AM, Osborne, Chris <Chris.Osborne_at_sky.uk> wrote:
>
> Hi All,
>
> I was wondering if someone could maybe help me out with an unusual observation I have on a couple of test systems.
> I have a user reporting that they are seeing differences in performance between the database on a VM (which is running ‘fast’) and a database on a physical (which is running slow)
>
> They are performing a load from MongoDB via a PHP app into the oracle database. In both tests the same source database is being used.
>
> I’ve done a quick overview on each of the systems and the only thing that is jumping out at me is that on the faster DB the log file sync time is much lower on the faster one. (the output was gather using oratop) Both DB’s are 12.1.0.2. The faster one is on CentOS 6.6 and the Slower one on Redhat 5.11.
>
>
> Slow DB
> EVENT (Real-Time) AVG: TOT WAITS TIME(s) AVG_MS PCT WAIT_CLASS
> log file parallel write 20008284 23783 1.2 100 System I/O
> log file sync 1730 9 5.2 0 Commit
> DB CPU 0 0
>
>
> Fast DB
> EVENT (Real-Time) AVG: TOT WAITS TIME(s) AVG_MS PCT WAIT_CLASS
> log file parallel write 20389439 28216 1.4 100 System I/O
> log file sync 179674 74 0.4 0 Commit
> SQL*Net message to client 7 0 0.0 0 Network
> DB CPU 0 0
>
> I’m also a bit confused as to how the log file sync time can be shorter than the log file write time.
>
> Any assistance or advice would be appreciated.
>
> Regards,
>
>
>
> Christopher Osborne
>
>
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Received on Thu Mar 24 2016 - 17:46:49 CET