same udpate statement takes same cpu time but significant different "sequential read wait time"

  • From: "qihua wu" <staywithpin@xxxxxxxxx>
  • To: oracle-l <oracle-l@xxxxxxxxxxxxx>
  • Date: Sat, 29 Sep 2007 15:15:53 -0700

We have one test database another production database, the data volumn
nearly the small. But a single update statement takes about 2,000 seconds on
test  database, but 7,000 seconds on the productoin database. For the report
of OEM, both test database and production database take about 1,500 seconds
on CPU. But the test database only takes 500 seconds on "sequential read"
and production database take 4,500 seconds on "sequential read".

So I ran the following sql on the both database, and found that single
sequential read wait time on production is much longer than test database.
And I am wondering whether the IO subsystem in production is not as good as
test.  What's your opinion on the big difference on "sequential read'?

BTW,The unix team and SAN team are not easy to appoach, so I must gather
evidence to please them look into the IO subsystem. The sql result is only
from database level and they won't look at any evidence from database level.
Is there any standard unix tool that can test the "sequential read' speed?

   sum(a.time_waited_micro)/sum(a.total_waits)/1000000 c1,
   sum(b.time_waited_micro)/sum(b.total_waits)/1000000 c2,
   dba_hist_system_event a,
   dba_hist_system_event b
   a.snap_id = b.snap_id
   a.event_name = 'db file scattered read'
   b.event_name = 'db file sequential read';

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