RE: weird behaviour for mreadtim < sreadtim in 10g
- From: "Christian Antognini" <Christian.Antognini@xxxxxxxxxxxx>
- To: <amit.poddar@xxxxxxxx>
- Date: Sun, 10 Sep 2006 18:02:27 +0200
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
--
//www.freelists.org/webpage/oracle-l
Other related posts:
