RE: I/O and db_file_multiblock_read_count
- From: "Baumgartel, Paul" <paul.baumgartel@xxxxxxxxxxxxxxxxx>
- To: "'kevinc@xxxxxxxxxxxxx'" <kevinc@xxxxxxxxxxxxx>, "oracle-l" <oracle-l@xxxxxxxxxxxxx>
- Date: Sat, 9 Dec 2006 14:17:38 -0500
Disk caching apparently can play havoc with results:
app/home/oracle > time dd if=/data/oracle/xxx/u01/xxx_11.dbf of=/dev/null
bs=131072
48008+1 records in
48008+1 records out
real 1m21.120s
user 0m0.180s
sys 1m14.020s
app/home/oracle > time dd if=/data/oracle/xxx/u01/xxx_11.dbf of=/dev/null
bs=262144
24004+1 records in
24004+1 records out
real 0m9.851s
user 0m0.020s
sys 0m9.830s
Re-running with bs=131072 completed in about 9 seconds as well. Perhaps best
to use different files (of same size) for each run?
Paul Baumgartel
CREDIT SUISSE
Information Technology
DBA & Admin - NY, KIGA 1
11 Madison Avenue
New York, NY 10010
USA
Phone 212.538.1143
paul.baumgartel@xxxxxxxxxxxxxxxxx
www.credit-suisse.com
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On
Behalf Of Kevin Closson
Sent: Friday, December 08, 2006 6:49 PM
To: kevin.lidh@xxxxxxxxx; oracle-l
Subject: RE: I/O and db_file_multiblock_read_count
do the "same" thing using dd. Whatever your db_block_size is, plug it in as
follows:
$ time dd if=<datafile_for_the tablespace> of=-/dev/null
bs=<block_size_in_bytes*16>
then re-run:
$ time dd if=<datafile_for_the tablespace> of=-/dev/null
bs=<block_size_in_bytes*128>
please let me know what you find
_____
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Kevin Lidh
Sent: Friday, December 08, 2006 12:46 PM
To: oracle-l
Subject: I/O and db_file_multiblock_read_count
I was reading an article about the appropriate setting for
db_file_multiblock_read_count. I'm on a HP-UX 11.11 64-bit system with Oracle
9.2.0.7.0. The original value was 16 and I bounced the database and ran a
million record full-scan test (10046 trace) and then set the value to 128 (max
value) and re-ran the
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