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Home -> Community -> Mailing Lists -> Oracle-L -> RE: weird behaviour for mreadtim < sreadtim in 10g
Amit
> My question is what calculation 10g is using for calculating FTS
> cost when mreadtim < sreadtim.
When mreadtim <= sreadtim the query optimizer fall back to the computation used with no workload system stats. Once I tried to find out how the computation is done... The best I found was:
I/O cost = blocks / ( 1 + A*ln(MBRC) + B*ln(MBRC)^2 + ... )
Notes:
- A and B depends on IOSEEKTIM and IOTFRSPEED - MBRC is used, not DB_FILE_MULTIBLOCK_READ_COUNT - In any case with system stats Wolfgang's formula is no more valid - In 9i neither IOSEEKTIM nor IOTFRSPEED exist...
HTH
Chris
-- http://www.freelists.org/webpage/oracle-lReceived on Sun Sep 10 2006 - 11:02:27 CDT
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