RE: db_file_multiblock_read_count and performance

Do you get a different plan when you change the parameter?

Are you doing any physical IO with your test query?

I thought your OS will always do whatever it is capable of, so changing this parameter will only effect the cost of the different plans Oracle comes up with.

Suggest you read "Searching for intelligent life in cost based optimizer" (search google) and adjust optimizer parms correctly, also set MBRC to whatever OS is capable of, search ixora (Steve Adam's site) for a script that will determine this.=20

-----Original Message-----

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of ryan_gaffuri_at_comcast.net
Sent: Monday, December 06, 2004 11:21 AM To: Oracle-L_at_freelists.org
Subject: db_file_multiblock_read_count and performance

I have been testing this extensively over the last few months. I do a full table scan with a db_file_multiblock_read_count =3D 1 and then one = =3D
128( i check the 10046 trace to verify i am getting this much) and I see absolutely no difference whatsoever in response time.=20 i am doing=20
select count(*)
from heap_table;
I have tested this on windows xp, solaris, with EMC, netapp, and regular old cheap off the shelf hard drives. I have tested it in 8.1.7, 9.0,9.1,9.2.
has anyone see a response time improvement from this parameter anywhere?

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http://www.freelists.org/webpage/oracle-l Received on Mon Dec 06 2004 - 11:50:24 CST