Tuesday Jul 11, 2006

Threshold login triggers for Oracle 10046 event trace collection

There are multiple ways to gather trace data. You can instrument the application, pick an oracle sid from sysdba, turn on tracing for all users (ouch), or use a login trigger to narrow down to a specific user. Each of these methods have merit, but recently I desired to gather traces at various user levels.

The problem with most packaged applications, is that they all use the \*same\* userid. For this Oracle 10G environment, I used this fact to filter only connections of the type that I wanted to sample. I wanted to gather 10046 event trace data when the number of connections was 10, 20, or 30. To achieve this, I used a logon trigger and sampled the number of sessions from v$session to come up with the connection count. I have found this little trick to be very useful in automating collection without modifying the application. I hope this can be useful to you as well.

create or replace trigger trace_my_user
  after logon on database

DECLARE
  mycnt  int;

BEGIN

SELECT count(\*)
 INTO mycnt
 FROM v$session
 WHERE username='GLENNF';

 if (user='GLENNF') and ((mycnt=10) or (mycnt=20) or (mycnt=30)) then
   dbms_monitor.session_trace_enable(null,null,true,true);
 end if;
end;
/

Tuesday Jun 21, 2005

"orasrp" - Free Oracle response time based trace profiler.

Ever since I started reading the "Optimizing Oracle Performance" book by Cary Millsap, I have been salivating over getting a copy of the Hotsos profiler - but alas it is too expensive. Recently I tried to find a copy of their free version "Sparky" but it had been pulled due to support issues.

Finally, I stumbled upon orasrp. This analyzer is written in python and can be used standalone to produce html, or you can browse a directory of trace files via your web browser.
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This blog discusses performance topics as running on Sun servers. The main focus is in database performance and architecture but other topics can and will creep in.

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