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RE: buffer busy waits PUZZLES - is there actually a problem?

From: Mark W. Farnham <>
Date: Wed, 18 May 2005 08:13:21 -0400
Message-ID: <>

Did your transactional throughput go up, down, or not change much?

Asked another way, are these higher waits insignificant side effects of un-jambing some other problem?

It is not possible to know without the times, and even with the times, we cannot know whether this is a problem or simply a report of a change in statistics unless you tells us whether throughput is now changed, and how.

Asked yet another way, is some process materially slower than you need it to be due to the amount of TIME spent waiting for these waits.

Abstract attempts to change the values of statistics reports from running systems without correlation to a process or task that is running slower than required have little (little includes nothing) to do with making things actually process faster.

Collection and observation of some statistics without correlation to problem processes can be useful, but that is part of capacity planning and load management, not optimization. Even then (unless you're using systems statistics as a proxy for company business growth in an attempt to predict stock outcomes or something like that) you need to correlate the statistics you observe to known scaling limits of your existing environment.

So, are you trying to fix some process that is going slower than you think it should (or more appropriately, slower than your service level requirement),
or are you just trying to manipulate the statistics?

Now I will not deprecate that activity if you're doing it as a learning exercise or even if you're just servicing your CTD. But I would like to know if you have a throughput problem you're trying to solve (or not).

To answer your question, if changes you made ungated pent up demand for these tables, sure, you could have driven the load on the tables higher. If your throughput went up, then the higher frequency of wait events is a happy side effect. If your throughput went down, the times and a correlation with the now slower process(es) *might* show that the increase in waits represents a problem to solve.



-----Original Message-----
[]On Behalf Of The Human Fly Sent: Wednesday, May 18, 2005 2:11 AM
Cc:; Oracle-L Freelists Subject: Re: buffer busy waits PUZZLES

However, I haven't have buffer busy wait as my tops events nor I see any session execessively waiting for this event. I have already mentioned in my previous replies that I have grabbed these values from v$segment_statistics dynamic view.

The following are today's result for the buffer busy waits.

TRANSACTION_LOG                    211143
FM_AUDIT_FORM                       39906
C_INTIMATION                        37029
CIS_AUDIT_TRAILH                    15001
C_CUSTOMER                           5793
FM_OLTP_LOG                          2727
RB_RESTRAINTS                        2239
SYSTEM_PARAMETER_VALUE               1492
RB_TRAN_HIST                         1102

I have increased default freelist 1 to 5 to those tables and now I can clearly see that those tables buffer busy wait event has increased madly. This could be due to heavy access on those tables?

However, I have been reading Cary's book past 1 year and still I enjoying reading it. Thank god, now, I started undertanding the concept behind method R and the true power of 10046 trace for resolving performance issues.

On 5/18/05, Alex Gorbachev <> wrote:
> My bad...


> 2005/5/17, Cary Millsap <>:
> > Ah! Credit to Gaja and Kirti for that one...
> >=3D20
> > Cary Millsap
> > Hotsos Enterprises, Ltd.
> >
> > * Nullius in verba *
> >=3D20
> > Visit for curriculum and schedule details...
> >=3D20
> >=3D20
> > -----Original Message-----
> > From: [mailto:oracle-l-bounce_at_freelists.o=
> ]
> > On Behalf Of Alex Gorbachev
> > Sent: Tuesday, May 17, 2005 2:42 PM
> > To:
> > Cc: K Gopalakrishnan;
> > Subject: Re: buffer busy waits PUZZLES
> >=3D20
> > sessions/transactions than you you've got CTD ("Compulsive Tuning
> > Disorder") speaking Carry's language.

> --=3D20
> Best regards,
> Alex Gorbachev
> --

Best Regards,
Jaffar, OCP DBA
Banque Saudi Fransi
Saudi Arabia


"It is your atittude, not your aptitude that determins your altitude."

Received on Wed May 18 2005 - 08:20:30 CDT

Original text of this message