Re: Unknown Exadata Cell Parameter - "_cell_fc_toresilver_limit_chdrs"

Out of curiosity, did you tried to measure the performance (defined as duration) of a set queries with and without this parameter set?

Thanks

On Thu, Dec 14, 2023, 22:22 Osman DINC <dinch.osman_at_gmail.com> wrote:

> Hi all Oracle enthusiasts,
>
> Do you have any information about the "_cell_fc_toresilver_limit_chdrs"
> parameter?
> It is set on my environment (X7-2) cellinit.ora. It is an undocumented and
> non-default configuration.
>
> I could not find any information about it, but it is commented as "It is
> set to reduce Internal IO on exadata cells". We do not have prior knowledge
> about it.
>
> Also I have screenshots of *AWR reports - Exadata Statistics - Top IO
> Reasons by MB * section.
> (Before and after parameter change)
>
> Before _cell_fc_toresilver_limit_chdrs parameter is set:
>
> https://drive.google.com/file/d/1PEcjUYAuG8SNTq1vfXLl0fyoeoffSLhq/view?usp=drive_link
>
> After "_cell_fc_toresilver_limit_chdrs"=6000000
>
> https://drive.google.com/file/d/12tDsDvt22oFyEaQtRdMsXcCYduw9992A/view?usp=drive_link
>
> According to the screenshots, It reduces Internal IO done by storage
> servers dramatically, but there may be a trade-off which i do not know.
>
> I want to clear this parameter as it is a non-default configuration. It
> was set on image version 20.1.5.0.0.201209 and it has been retained for
> years.
>
> Exadata image version is 22.1.17 now.
> If anybody can share more information about what this parameter does, I
> will be glad.
>
>
> Regards,
> Osman DİNÇ.
>
>
>

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