RE: Performance Problems

  • From: "Ebadi, Abdul" <Abdul.Ebadi@xxxxxxxxxx>
  • To: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
  • Date: Thu, 23 Mar 2006 10:29:03 -0700

Optimizer mode is CHOOSE.  We have not gathered stats on the data
dictionary.  Last_analyzed is null for all SYS/SYSTEM-owned tables.


-----Original Message-----
From: Bobak, Mark [mailto:Mark.Bobak@xxxxxxxxxxxxxxx] 
Sent: Thursday, March 23, 2006 10:24 AM
To: Ebadi, Abdul; oracle-l@xxxxxxxxxxxxx
Subject: RE: Performance Problems

What is optimizer_mode set to?

Have you tried the query with a /*+ RULE */ hint?

Have you considered gathering statistics on the data dictionary?


Mark J. Bobak
Senior Oracle Architect
ProQuest Information & Learning

For a successful technology, reality must take precedence over public
relations, for Nature cannot be fooled.  --Richard P. Feynman, 1918-1988

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Ebadi, Abdul
Sent: Thursday, March 23, 2006 12:20 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Performance Problems

We have a large datawarehouse database on Oracle and are encountering
strange performance problems.  A query such as "select count(*) from
dba_data_files;" will run in a few seconds or as long as 15 minutes
depending on when this is run.  We've narrowed it down to where it is
not even directly related to load on the DB.  A few days ago, I ran this
query right after we started the DB (no activity in the DB at all) and
it took 6 minutes!  The waits we were seeing were "db file sequential
read" and "buffer busy wait" for this query.  Keep in mind our DB is
~27TB with ~30,000 datafiles!

Oracle on Solaris 10.   

Any help will be appreciated.



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