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RE: "free buffer waits" under eXtreme Transaction Loads

From: VIVEK_SHARMA <VIVEK_SHARMA_at_infosys.com>
Date: Mon, 2 Aug 2004 13:30:06 +0530
Message-ID: <F0CB3C9983B77E4AB4ADEFA63DAB109F0EFA4F8F@twrmsg03.ad.infosys.com>


Some OBSERVATIONS:-
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

  1. Reduced "free buffer waits" by:-
  2. REDUCING log_checkpoint_interval to a fraction of the Total ONLINE REDO LOG FILE Size (NOTE - log_checkpoint_timeout=3D0)
  3. Putting undo Tablespace onto Raw
  4. "free buffer waits" & "log file sync" are unrelated

NOTE - Only Online Redo logfiles & Undo on RAW. Rest of Database on VXFS (Mounted FS)
Transactions - OLTP in Nature of Banking Application on Oracle 9.2.0.5/HP-UX 11i

HTH P.S. Thanks again one & all for the Support

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Gaja Krishna Vaidyanatha
Sent: Tuesday, July 27, 2004 12:49 AM
To: oracle-l_at_freelists.org
Subject: Re: "free buffer waits" under eXtreme Transaction Loads

Vivek,

Could you please share with us a 10046 trace output on the said SQL statements, so that one can ascertain what the "real problem" is? Just by looking at the STATSPACK report and the high-level waits, it is very difficult to determine anything, at the level of granularity one needs.

Some questions you need to ask yourself:

  1. What is your tuning goal?
  2. What is an acceptable response time for each of your SQL statements?
  3. What is the quantifiable benefit of your tuning exercise? -- Business Value for the Bank

If the SQL statements run within the "required response times" during heavy/peak load, then no matter what the "waits" are, should one really care? One can try eliminating every wait in the database, but may never accomplish that goal. Also, if one consciously tries "eliminating waits" even though the application is running within its response time goals - One is probably suffering from CTD... Compulsive Tuning Disorder...:)

Jokes aside, response time and business value for the tuning exercise are key elements. Everything else is secondary. I am optimistic that you have already considered that.

Cheers,

Gaja


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Received on Mon Aug 02 2004 - 02:57:14 CDT

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