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I have high "db file scattered read" times and not sure where to start by fixing it

Posted on 2006-06-23
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As you can see below heavy wait times on actually everything not sure where to start on this one, can anybody point me in the right direction?

Event      Total waits      Waits/s      % total      Total wait time      Wait time/s      %  total      Avg Wait
db file scattered read      1,427,013      66.65      79.40      10,003,740.00      443.06      22.25      6.65
SQL*Net break/reset to client      104      0.00      0.00      435,080.00      0.00      0.00      0.00
db file sequential read      496,018      2.66      3.16      213,150.00      6.48      0.33      2.44
buffer busy waits      455      5.89      7.02      75,730.00      1,533.23      77.00      260.11
SQL*Net more data to client      926,010      0.00      0.00      67,180.00      0.00      0.00      0.00
enqueue      27      0.00      0.00      27,890.00      0.00      0.00      0.00
control file parallel write      34,268      0.32      0.39      25,970.00      0.00      0.00      0.00
control file sequential read      133,178      0.06      0.08      23,590.00      0.00      0.00      0.00
log file parallel write      5,295      0.19      0.23      14,630.00      0.00      0.00      0.00
log file sync      4,222      0.19      0.23      13,530.00      0.00      0.00      0.00
latch free      573      0.52      0.62      11,590.00      8.42      0.42      16.25
log file switch (checkpoint incomplete)      14      0.00      0.00      9,470.00      0.00      0.00      0.00
log file switch (archiving needed)      14      0.00      0.00      9,340.00      0.00      0.00      0.00
log file switch completion      66      0.00      0.00      6,940.00      0.00      0.00      0.00
SQL*Net message to client      1,339,510      3.89      4.63      6,580.00      0.00      0.00      0.00
file open      4,788      0.00      0.00      6,160.00      0.00      0.00      0.00
direct path read      33,171      2.91      3.47      5,090.00      0.00      0.00      0.00
log file sequential read      1,282      0.00      0.00      2,480.00      0.00      0.00      0.00
log buffer space      5      0.00      0.00      1,830.00      0.00      0.00      0.00
refresh controlfile command      16,540      0.00      0.00      1,300.00      0.00      0.00      0.00
direct path write      3,778      0.65      0.77      520.00      0.00      0.00      0.00
file identify      399      0.00      0.00      230.00      0.00      0.00      0.00
process startup      1      0.00      0.00      80.00      0.00      0.00      0.00
log file single write      146      0.00      0.00      80.00      0.00      0.00      0.00
LGWR wait for redo copy      11      0.00      0.00      10.00      0.00      0.00      0.00
library cache pin      3      0.00      0.00      10.00      0.00      0.00      0.00
db file parallel write      922      0.00      0.00      0.00      0.00      0.00      0.00
SQL*Net more data from client      116      0.00      0.00      0.00      0.00      0.00      0.00
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Question by:sea2sky
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3 Comments
 
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by:MohanKNair
ID: 16981450
The statspack report shows the TOP 5 wait events. What are those events? Pay more attention to those and analyze how to reduce the waits.
Also compare the statspack report when the database is functioning normally and during the activity period.
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by:shahidns
ID: 17000508
Try rebuilding all your indexes for a change. This should solve some of the problem.
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sudhi022299 earned 750 total points
ID: 17041256
I wouldn't go straight to rebuilding the indexes. As mentioned by MohanKNair, I would start with the 'Top 5' and go from there. Even in a perfectly *acceptable* running systems, there are bound to be i/o events. So don't just jump to them and start changing things. The things that should give you a clue are:

1. Top 5 wait events of statspack report.
2. Top SQLs doing lot of logical IO's
3. Top SQLs consuming memory (if memory consumption is of a concern)
...

Also don't forget to dig answers for "From when did things go to an unacceptable state?" "What was the time values of an acceptable state" etc.

Have fun tuning.
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