Re: Buffer Pool Testing

At a high level, I think the various pools operate in pretty much the same way - but there are some differences, some of which may be affected by various hidden parameters.

For example, Steve Adams has this note (dated Oct 2000) on his website as one of several observations on the 'new' LRU mechanism. Some details may have evolved since then, of course, but it is a good indication of how the pools can be "the same, but different".

<quote>

    By default, the KEEP and RECYCLE buffer pools do not have a hot region,

    but this can be changed by setting the _db_percent_hot_keep and     _db_percent_hot_recycle parameters to non-zero values.     Otherwise, the RECYCLE buffer pool has exactly the same LRU     semantics as the DEFAULT buffer pool - it is only the name that     is different - and the KEEP buffer pool differs only in that buffers

    read for long table scans are cached just below the hot region     rather than at the LRU end and consistent read buffers are immediately

    frozen.
</quote>

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 03 January 2003 02:23

>2. The KEEP and RECYCLE Pools aren't really special in any sense: the
buffer
>algorithms are the same for these as for the DEFAULT pool - it is
just that
>these pools are named so that tables can be defaulted to load into
any one
>of them. By using this feature judiciously, you might be able to
avoid the
>problems of unneccesary buffering during FTS on tables smaller than
the
>threshhold without actually changing the undocumented parameter.
>
>Jonathan: Awaiting your expert comments on this new twist :)
>

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Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

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