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Hello,
I tried to find the following statement cost :
select * from T1
T1 is composed of : 22064 blocks and the db_file_multiblock_read_count=64.
For full scan, I used : Cost = blocks/db_file_multiblock_read_count
and so the cost is around 345
Using autotrace, the cost given by Oracle is about 850...
I did the test with db_file_multiblock_read_count=32. Oracle find about 1700 (my value is 850).
Any explanation ? How Oracle find 850 ?
(blocks = 22064, empty block = 1240, db_block_size=4ko, 30o/rows, 850000 rows...).
thanks in advance
Sofiane
Sofiane
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Inasmuch as I admire your effort, I fear it is in vain. The Cost that Oracle calculates is useful only to itself, and holds no relationship to the real world.
Here are just a couple of the threads where we have addressed the value of 'COST'
http://www.dbasupport.com/forums/sho...threadid=12384
http://www.dbasupport.com/forums/sho...threadid=11868
- Chris
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