*From*: "Polarski, Bernard" <Bernard.Polarski@xxxxxxxxxxxxxx>*To*: <oracle-l@xxxxxxxxxxxxx>*Date*: Wed, 27 Sep 2006 11:20:41 +0200

Sorry for my previous mail was sent before I completed it due to me hitting bad keystroke Here is what I want to express: If I have a rowset of 20, and avg block of 31 and the best CF possible, then I will access only one block, maybe two if my rowset overspill a block boundary. And If my clustering factor is the worst possible then I will access 20 table blocks. So for a table total count block of 345, rownum of 32000 and CF of 345 ( best case), given a rowset of 20 I will access at most 2 blocks Again for a table total count block of 345, rownum of 32000 and CF of 32000 (worst case), rowset of 20 I will access 20 blocks. So I derived the following formula ( index clustering factor / table blocks) / (table num rows/table blocks) = table block accessed I obtain 1% in the best case wheen CF = table blocks I get 100% in the worst case when CF = table num_rows : (345/345) / (32000/345) * 100 = .011623535 (32000/345)/(32000/345) * 100 = 100 Let's call this ratio R Obiously I can retrieve the min and max, but still given the same rowset if I am told that the CF is now 45% how does it translate ? Can we assume that I will access the number of table block equal to 45% of my index rowset of 20, say that predicted table acces block will be equal to (rowset/R*100) so here 20/45*100=9 blocks? B. Polarski

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