access IO by M/M/m Module

From: Sidney Chen <huanshengchen_at_gmail.com>
Date: Tue, 27 Sep 2011 11:17:13 +0800
Message-ID: <CAM_ddu8G7QCtLTfGgF+GYFz-udNXUZk=BwLzxjqnt9MsD7MexQ_at_mail.gmail.com>

Hi,
When reading the Topic of M/M/m Module in the book <<Optimizing Oracle Performance>> by Gary Millsap, I have the idea to verify if our I/O subsystem can fit the M/M/m module.

The db is IO intense, 80% db time is spent on "db file sequential read",  and the avg wait time is 15ms.
1. to do the assessment, I extract 3357 lines in one 10046 trace file 2. compute the ela time as second(divide by 1000000, keep the distribution compact)
3. using the mdist.pl to tell if the elapse time for "db file sequential read" fit the "exponential distribution".

the result is reject, so i wonder if there are accurate methods to assess. Any advise is appreciated.

oracle: ~/scripts$ perl mdist.pl 2.lst

 Hypothesis: Data are exponentially distributed with mean 0.0155063946976467
Test result: n=2 V=1143.25 p=1.000
    Verdict: *Reject*

--original record in 10046 trace file

WAIT #19: nam='db file sequential read' ela= 26431 file#=207 block#=258517
blocks=1 obj#=206447 tim=1284706983664908
WAIT #19: nam='db file sequential read' ela= 11191 file#=108 block#=1351954
blocks=1 obj#=206444 tim=1284706983677002
WAIT #19: nam='db file sequential read' ela= 11836 file#=25 block#=294842
blocks=1 obj#=206444 tim=1284706983689523
WAIT #19: nam='db file sequential read' ela= 6268 file#=25 block#=472857
blocks=1 obj#=206444 tim=1284706983696181
WAIT #19: nam='db file sequential read' ela= 6339 file#=108 block#=1348802
blocks=1 obj#=206444 tim=1284706983702664
WAIT #19: nam='db file sequential read' ela= 7363 file#=25 block#=434781
blocks=1 obj#=206444 tim=1284706983710368
WAIT #19: nam='db file sequential read' ela= 12006 file#=176 block#=489651
blocks=1 obj#=206444 tim=1284706983722477
WAIT #19: nam='db file sequential read' ela= 18163 file#=107 block#=1728592
blocks=1 obj#=206444 tim=1284706983740767
WAIT #19: nam='db file sequential read' ela= 24003 file#=107 block#=1740869
blocks=1 obj#=206444 tim=1284706983765194
WAIT #19: nam='db file sequential read' ela= 4780 file#=25 block#=473096
blocks=1 obj#=206444 tim=1284706983770782
WAIT #19: nam='db file sequential read' ela= 6644 file#=25 block#=431224
blocks=1 obj#=206444 tim=1284706983777508
WAIT #19: nam='db file sequential read' ela= 20201 file#=107 block#=1747395
blocks=1 obj#=206444 tim=1284706983797791

WAIT #5: nam='db file sequential read' ela= 89939 file#=207 block#=359305 blocks=1 obj#=206447 tim=1284706984136333 WAIT #5: nam='db file sequential read' ela= 21708 file#=25 block#=292852 blocks=1 obj#=206444 tim=1284706984158777

--record in 2.lst, ela divided by 1000000
.026431
.011191
.011836
.006268
.006339
.007363
.012006
.018163
.024003
.00478
.006644
.020201
.089939
.021708

-- 
Sidney Chen
Blog: *http://sid.gd* <http://sid.gd>


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Received on Mon Sep 26 2011 - 22:17:13 CDT