Re: db buffer cache advisory clarification

Stephen,

This is for a 15 minute snapshot?  It seems a little strange to me.
>         Size for  Size      Buffers for  Est Physical          Estimated
> P   Estimate (M) Factr         Estimate   Read Factor     Physical Reads
> --- ------------ ----- ---------------- ------------- ------------------
> D             64   1.0            7,940          1.00        937,436,311

937436311/(15*60)=1041595.9 or over 1 million physical reads per second.

Maybe something else is going on?

Steven

On 3/28/06, Stephen Anderson <st.anderson@xxxxxxxxx> wrote:
>
> Can anyone let me know why the advisory is saying i can so drastically
> reduce my PIO's by reducing my db_cache_size? I have looked around the web
> and have never seen an explanation for this.  I also looked on metalink to
> see if it was a know bug.
>
>
> This was from a lvl 5 statspack 15 minute snap on 9.2.0.3 on Sun Solaris.
> The instance has been up for over 8 months.  The results are the same no
> matter when I snap.
>
> Buffer Pool Advisory for DB: MERLIN  Instance: MERLIN  End Snap: 15
> -> Only rows with estimated physical reads >0 are displayed
> -> ordered by Block Size, Buffers For Estimate
>
>
>         Size for  Size      Buffers for  Est Physical          Estimated
> P   Estimate (M) Factr         Estimate   Read Factor     Physical Reads
> --- ------------ ----- ---------------- ------------- ------------------
> D             16    .3            1,985          0.06         54,232,173
> D             32    .5            3,970          0.03         28,255,991
> D             48    .8            5,955          0.01          7,094,145
> D             64   1.0            7,940          1.00        937,436,311
> D             80   1.3            9,925          0.99        924,356,448
> D             96   1.5           11,910          0.97        912,150,561
> ...
> D            272   4.3           33,745          0.85        792,237,723
> D            288   4.5           35,730          0.84        783,014,854
> D            304   4.8           37,715          0.82        769,676,998
> D            320   5.0           39,700          0.79        738,539,663
>
> -------------------------------------------------------------
>
> Regards,
> Steve Anderson
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