RE: UncompBkts: what is it? (reference to 10053 trace)
- From: "Schultz, Charles" <sac@xxxxxxxxxxxxx>
- To: "John Kanagaraj" <john.kanagaraj@xxxxxxxxx>
- Date: Fri, 28 Jul 2006 08:12:29 -0500
Thanks, Mark and John, much appreciated!
However, I still do not know what UncompBkts are. I have to infer that
they have something to do with buckets. Uncompressed? If so, what does
that mean? The numerical value is often close to the number of rows, but
I do not know what the information implies.
________________________________
From: John Kanagaraj [mailto:john.kanagaraj@xxxxxxxxx]
Sent: Thursday, July 27, 2006 6:03 PM
To: Schultz, Charles
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: UncompBkts: what is it? (reference to 10053 trace)
Charles,
Oracle Applications has a standard formula to determine if a Column is
worth having a Histogram: If a single value occupies 1/75th or more of
the sample, and the count(*) is > 3000, then a histogram is recommended.
For you OraApps DBAs out there, look at the definition of
APPS.FND_STATS.CHECK_HISTOGRAM_COLS. For the others, look at 358323.1
<http://metalink.oracle.com/metalink/plsql/ml2_documents.showDocument?p_
database_id=NOT&p_id=358323.1>
John Kanagaraj
On 7/27/06, Schultz, Charles <sac@xxxxxxxxxxxxx> wrote:
Google did not deign to tell me, so I am looking elsewhere.
In somewhat related terms, is there a set mathematical formula
for "data skew"? Folks talk about a "little skew" or "very skewed" data.
Practically any column is going to have at least some skew, but I have
to assume that there is a threshold whereby a given histogram (ie,
insufficient number of buckets) is going to hurt your performance.
charles schultz
oracle dba
aits - adsd
university of illinois
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John Kanagaraj <><
DB Soft Inc
Phone: 408-970-7002 (W)
Fear connects you to the Negative, but Faith connects you to the
Positive! I Jn 4:18
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