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Home -> Community -> Mailing Lists -> Oracle-L -> RE: db buffer cache advisory clarification
Hi Stephen,
As for your question on consistency of the report for small cache
values, I think you still have a formatting problem. If you take row N.3
for example, the column "Est Physical Read Factor" tells you that the
value there is 1/0.02=50 times bigger than what is reported in row N.4,
that is the cache advisor expects 50 billion physical reads (your
sqlplus format string handles numbers up to 10 billion)
Your next problem is to make any sense of those huge numbers..
Cheers,
Luca
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Stephen Anderson
Sent: Wednesday, March 29, 2006 11:28 AM
To: jungwolf
Cc: oracle-l_at_freelists.org
Subject: Re: db buffer cache advisory clarification
Hello,
Ran a 7 minute snap this morning - results are getting worse! Physical Reads are at 6278/s and Logical Reads are 70,844/s.
Buffer Pool Advisory for DB: MERLIN Instance: MERLIN End Snap: 31
-> 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 0.07 124,118,645
D 32 .5 3,970 0.04 70,906,440
D 48 .8 5,955 0.02 29,259,452
D 64 1.0 7,940 1.00 1,783,067,416
D 80 1.3 9,925 0.99 1,757,988,089
...
D 256 4.0 31,760 0.85 1,523,232,446
D 272 4.3 33,745 0.85 1,507,672,223
Now we can see over 1 billion PIO's, so it cannot be a formatting thing. The metalink note that Jared suggested merely chose to format it differently.
On 3/28/06, jungwolf <spatenau_at_gmail.com> wrote:
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 1.00937,436,311
937436311/(15*60)=1041595.9 or over 1 million physical reads per second.
Maybe something else is going on?
Steven
-- http://www.freelists.org/webpage/oracle-lReceived on Wed Mar 29 2006 - 04:11:20 CST
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