Re: More Memory the better ...Why not

From: Tanel Poder <change_to_my_first_name_at_integrid.info>
Date: Tue, 26 Aug 2003 09:49:45 +0300
Message-ID: <3f4b030a$1_1@news.estpak.ee>

"Franklin" <member29243_at_dbforums.com> wrote in message news:3283899.1061860214_at_dbforums.com...
>
> Well, how about using a 10 gig db_cache_size?
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>
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> Is there such a thing as too much data buffer RAM?
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>
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> Actually, all data buffer RAM is hashed, so size is not an issue
> there, BUT you can degrade performance with a super-sized
> db_cache_size is when:
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>
>
> 1 - You have heavy use of temp tables, truncates or data purging -
> Oracle must sweep all blocks in the data buffer to clean-out
> inval;id blocks

There is a partial checkpoint done when segment is dropped, is it the case with temp tables as well? Can you point me to source of this information?

> 2 - High updates - The DBWR must scan the whole data buffer looking for
> dirty blocks, causing high work for the DBWR process.

No it doesn't. There is a parameter _db_block_max_scan_pct which sets the percentage of buffers to inspect when looking for free (used to be _db_block_max_scan_cnt IIRC).

Tanel. Received on Tue Aug 26 2003 - 01:49:45 CDT