RE: UncompBkts: what is it? (reference to 10053 trace)

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_at_gmail.com] Sent: Thursday, July 27, 2006 6:03 PM
To: Schultz, Charles
Cc: oracle-l_at_freelists.org
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_at_uillinois.edu> 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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