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rubs_65
Posting Yak Master
144 Posts |
 Posted - 2004-02-09 : 14:03:49
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| Hi,What is difference between information that we get from scan density and columns (extents scanned and extents switches). For example for a particular table I got the following result. Here scan density is 75% whereas extents scanned/switches looks good.- Extents Scanned..............................: 100- Extent Switches..............................: 99- Avg. Pages per Extent........................: 5.9- Scan Density [Best Count:Actual Count].......: 75.00% [75:100]Thanks--Harvinder |
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tkizer
Almighty SQL Goddess
38200 Posts |
Posted - 2004-02-09 : 14:07:27
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Does this help:From BOL"quote:
The fragmentation level of an index can be determined in two ways: Comparing the values of Extent Switches and Extents Scanned. Note: This method of determining fragmentation does not work if the index spans multiple files. The value of Extent Switches should be as close as possible to that of Extents Scanned. This ratio is calculated as the Scan Density value, which should be as high as possible. This can be improved by either method of reducing fragmentation discussed earlier.Understanding Logical Scan Fragmentation and Extent Scan Fragmentation values. Logical Scan Fragmentation and, to a lesser extent, Extent Scan Fragmentation values give the best indication of a table's fragmentation level. Both these values should be as close to zero as possible (although a value from 0% through 10% may be acceptable). It should be noted that the Extent Scan Fragmentation value will be high if the index spans multiple files. Both methods of reducing fragmentation can be used to reduce these values.
Tara |
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rubs_65
Posting Yak Master
144 Posts |
Posted - 2004-02-09 : 14:11:37
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| Tara,It still doesn't clear to me. I have only 1 database file so why still there is difference between 2 sets of values.Thanks--Harvinder |
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tkizer
Almighty SQL Goddess
38200 Posts |
Posted - 2004-02-09 : 14:28:41
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| http://www.sql-server-performance.com/dt_dbcc_showcontig.aspTara |
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DBCC SHOWCONTIG question