Oracle-L: RE: RE: db file sequential read

From: VIVEK_SHARMA <VIVEK_SHARMA_at_infosys.com>
Date: Wed, 20 Nov 2002 05:38:26 -0800
Message-ID: <F001.00507C21.20021120053826@fatcity.com>

Yes , did some small benchmarks of a Batch process running for a Few minutes & Loading the CPUs by 50 %

Database Exists on Veritas Filesystems (VXFS)

truss of the process Both application & Database Calls made

Run with Value of vxio:vol_maxio = 512 ( = 256 K [Default] )

Functions with the MAX Number of "calls" & sys time in "seconds" only shown below .

syscall              seconds   calls  errors
read                   23.19  355514
write                  23.11  323662
brk                     3.70   39354
lseek                   1.13   32078
llseek                  5.52  217075    113
pread64                 6.62  100393

NOTE - "100393" Calls made by system Function "pread64" Corresponds to "db file sequential read" of Oracle

Run - with Value of vxio:vol_maxio = 16384 ( = 8M ) - repeated the Run

syscall              seconds   calls  errors
read                   24.05  355613
write                  24.05  324018
brk                     4.09   40657
lseek                   1.23   32077
llseek                  6.05  217076    113
pread64                 6.16   96573

"96573" Calls made by system Function "pread64" which are less than "100393"

You can also Check metalink for relavence of this parameter for reducing "pread64" system function call

HTH -----Original Message-----
Sent: Wednesday, November 20, 2002 2:59 PM To: Multiple recipients of list ORACLE-L

VIVEK_SHARMA,

		Hi, did you have benchmark result or other whitepaper talking about this thoery?
		For db file sequential read, it is single block read to index and then to table, so i think enlarge the maxio size of the os won't help?(I just guess, did not test it).
		Enableing AIO or using raw device maybe will help io performance, thus give reduced io wait, i think.
	Good luck

Regards
zhu chao
Eachnet DBA
86-21-32174588-667
chao_ping_at_vip.163.com
www.happyit.net
www.cnoug.org(Chinese Oracle User Group)

2002-11-19 23:34:00 ,you wrote£º=======

>For "db file sequential read wait" Add Following to /etc/system
>On UFS
>Setting maxphys=8388608
>On VXFS
>set vxio:vol_maxio = 16384 ( implies 8MB )

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Author: VIVEK_SHARMA
  INET: VIVEK_SHARMA_at_infosys.com

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Received on Wed Nov 20 2002 - 07:38:26 CST