RE: buffer busy waits PUZZLES - is there actually a problem?
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: <sjaffarhussain@xxxxxxxxx>, <gorbyx@xxxxxxxxx>
- Date: Wed, 18 May 2005 08:13:21 -0400
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.
Regards,
mwf
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of The Human Fly
Sent: Wednesday, May 18, 2005 2:11 AM
To: gorbyx@xxxxxxxxx
Cc: Cary.Millsap@xxxxxxxxxx; 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
OUTWARD_CLEARING_CHEQUES 8310
C_CUSTOMER 5793
FM_OLTP_LOG 2727
INWARD_CLEARING_CHEQUES 2347
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 <gorbyx@xxxxxxxxx> wrote:
> My bad...
>=20
> 2005/5/17, Cary Millsap <Cary.Millsap@xxxxxxxxxx>:
> > Ah! Credit to Gaja and Kirti for that one...
> >=3D20
> > Cary Millsap
> > Hotsos Enterprises, Ltd.
> > http://www.hotsos.com
> > * Nullius in verba *
> >=3D20
> > Visit www.hotsos.com for curriculum and schedule details...
> >=3D20
> >=3D20
> > -----Original Message-----
> > From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxx=
rg=3D
> ]
> > On Behalf Of Alex Gorbachev
> > Sent: Tuesday, May 17, 2005 2:42 PM
> > To: sjaffarhussain@xxxxxxxxx
> > Cc: K Gopalakrishnan; oracle-l@xxxxxxxxxxxxx
> > Subject: Re: buffer busy waits PUZZLES
> >=3D20
> > sessions/transactions than you you've got CTD ("Compulsive Tuning
> > Disorder") speaking Carry's language.
>=20
> --=3D20
> Best regards,
> Alex Gorbachev
> --
> //www.freelists.org/webpage/oracle-l
>=20
--=20
Best Regards,
Jaffar, OCP DBA
Banque Saudi Fransi
Saudi Arabia
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