weird behaviour for mreadtim < sreadtim in 10g
- From: amit poddar <amit.poddar@xxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 08 Sep 2006 14:38:39 -0400
Hi,
I am struggling with a query performance issue which brought me to this
quandary about calculation of cost of full table scans when system stats
are enabled
Database Version: 10.2.0.2
Here are the details
Num Blocks in the table: 91872
mbrc 6
Mreadtim Sreadtim Cost
1 3 91864
1.1 3 91864
1.3 3 91864
1.8 3 91864
2.8 3 91864
3 3 91864
3.05 3 15569 (approximately =
91872/mbrc)
My question is what calculation 10g is using for calculating FTS cost
when mreadtim < sreadtim.
Because in 9i when mreadtim < sreadtim oracle seems to ignore the
system stats and calculates FTS cost as approximately (num_blocks/5.6)
(since db_file_multiblock_read_count is 8)
But 10.2 is behaving differently.
Any help would be appreciated
thanks
amit
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