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_at_gmail.com> 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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