Re: Large discrepancy between 'log file parallel write' and 'db file parallel write' times

From: Purav Chovatia <puravc_at_gmail.com>
Date: Wed, 2 Jan 2013 17:36:53 +0530
Message-ID: <CADrzpjGm7ejXrGpqo_h=5nGO8x1Wspn+k8dF3wgGPa=2TpKqZA_at_mail.gmail.com>

Hi John,
Is the behaviour specific to exadata or that is fully/partially true in case of ASM too? Does any kind of background I/O queue exist on non-exadata but ASM (RAC/non-RAC) based env.?

Thanks

On Mon, Dec 31, 2012 at 7:31 AM, John Clarke <john.clarke_at_centroid.com>wrote:

> Redo log and control file writes are considered "high priority" I/O
> consumers and get lumped into the high priority background I/O queue, so
> cellsrv will satisfy these requests at a higher priority than anything else.
> DBWR writes (which your db file parallel write waits is associated with)
> are prioritized the same as user I/O, relatively speaking, and a handful of
> other background-related writes and lower than log file/control file writes.
>
> Under heavy I/O load and saturation, this behavior should be what you may
> expect.
>
> - John
>
>

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Received on Wed Jan 02 2013 - 13:06:53 CET