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Re: Explain what is Oracle Logical IO

From: Niall Litchfield <n-litchfield_at_audit-commission.gov.uk>
Date: Wed, 27 Aug 2003 10:08:36 +0100
Message-ID: <3f4c7515$0$249$ed9e5944@reading.news.pipex.net>


"Billy Verreynne" <vslabs_at_onwe.co.za> wrote in message news:1a75df45.0308242142.1afdca96_at_posting.google.com...
> "Niall Litchfield" <niall.litchfield_at_dial.pipex.com>
>
> > > Logical I/O != Physical I/O
> >
> > But Physical I/O = Logical I/O ta da.
> >
> > Ok what I mean is logical I/O consists of *every* io request (usually
for a
> > database block read or update, but also logs etc) that Oracle makes.
> > Physical I/O are those io requests that result in a physical disk
access.
>
> True. We need to revise that formula of "Logical I/O != Physical I/O"
> to indicate that a logical i/o could result in a physical i/o even
> though it is not a physical i/o in itself.
>
> Which of course raises that pesky question.. just where the heck do
> all those deleted bytes go after a physical i/o has completed? After
> all, the number #1 rule in the universe is that nothing can be
> destroyed (the state merely change). Deleted bytes do not change into
> energy (I have yet to burn a disk due to too many deleted bytes). I've
> crawled around the bottom of the EMC array (with a magnifying glass)
> and have yet to see any of those deleted bytes. So what happens to
> them?

I have a theory on that. They make use of quantum entanglement to add bytes (most commonly zeros) to the bank balances of messers Ellison,Gates and McNealy :(

Cheers

-- 
Niall Litchfield
Oracle DBA
Audit Commission UK
Received on Wed Aug 27 2003 - 04:08:36 CDT

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