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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Your opinion please :) explanation of my point of view
RE: Your opinion please :) explanation of my point of viewThanks for the points
What tuning scenario does it not cover...
See Bob Lofstrand's email from yesterday... Determining Library Cache Usage... We are trying to tune the query with the following characteristics...
"when trying to run a monstrous 26.1kb query. Yes that is the amount of text. The one query involves 9 case statements, some nested in others and several involving more than 50 when clauses. It also has 8 sum(), over 200 to_date() and a group by clause... Don't ask."
at 8 point font, this query takes up just over 6 pages... and PART of the case statements are IN the group by. the only thing this thing doesn't have that we see 99% of the time is a decode. It will blow up in an EXPLAIN if the system is at all busy... and our biggest client (180 GB of data, biggest table involved is 38,000,000 rows) wants desperately to run it.
We have one instance on which it will PARSE... We are having fun now!!!!!!!!!
April Wells
Oracle DBA/Oracle Apps DBA
Corporate Systems
Amarillo Texas
@>-->-->--
"Few people really enjoy the simple pleasure of flying a kite"
Adam Wells age 11
"Imagination is the highest kite one can fly."
Lauren Bacall
-----Original Message-----
From: Juan Cachito Reyes Pacheco [mailto:jreyes_at_dazasoftware.com]
Sent: Thursday, February 26, 2004 1:33 PM
To: oracle-l_at_freelists.org
Subject: Re: Your opinion please :) explanation of my point of view
Yes, this resolves the 90% of tunning problems in standar database edition. The reason is simple, in STANDARD edition (no parallel execution, etc.) , at least here in Bolivia, you don't have lots and lots of users, maximum 20, the biggest table I have has 3,000,000 of records. So the tunning problems are not really serious in 9i.
Now I challenge you which tunning problem is not considered in that paper, and should be :=)
> Well, if your paper "solves 90% of tuning problems", than this list can
> rest peacefully...
>
> Igor Neyman, OCP DBA
> ineyman_at_perceptron.com
>
>
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Juan Cachito Reyes
> Pacheco
> Sent: Thursday, February 26, 2004 10:34 AM
> To: oracle-l_at_freelists.org
> Subject: Re: Your opinion please :) explanation of my point of view
>
> thanks to you, this will improve a lot, the point is that I don't have
> too
> much time.
>
> If you have something brief, for exapmle I got from Tom Kyte, "function
> in
> c+ can be up to 2 times faster", to have an idea when to use c and when
> not,
> or from tom kyte to "try to do in plsql, if you can't use java and if
> you
> can't use c++", this are the kind of guide and test takes looooong time
> to
> find.
> Even when some of you could think this is a list of tips I got randomly,
> it
> is not, in that paper there is all the tunning tips you need to solve
> 90% of
> tunning problems in standard edition, so don't think I take randomly
> some
> tips and put in a paper briefly and said "this is my paper"
> ----- Original Message -----
> From: "Freeman, Donald" <dofreeman_at_state.pa.us>
> To: <oracle-l_at_freelists.org>
> Sent: Thursday, February 26, 2004 11:24 AM
> Subject: RE: Your opinion please :) explanation of my point of view
>
>
> Let me chime in my 2 cents here. I printed and reviewed your document
> and
> noted a few
> things that I will discuss with my co-DBA. I liked the article because
> in a
> short
> document you summarized a number of things that were important in your
> experience. Some of
> them seem relevent to what I am doing so I will spend some time to check
> them out. As
> far as you posting it, I personally try to pass on tips and tricks as I
> learn them and I appreciate
> that behavior in others.
>
> As what we do is often a competitive business I have not often
> encountered
> people personally
> who freely give away valuable information which they struggled to gain.
> The
> top-level professionals
> who answer questions here are doing 'pro-bono' work for which I am
> grateful.
> It's the same advice
> that people pay them for. In real life I'm beginning to think it's
> pretty
> remarkable when somebody
> says, "Come on over, I'll show you how it works." The lists are very
> valuable to me. I'm not in a
> position to travel to conferences, seminars, and attend workshops to
> improve
> my skills and don't
> work for an employer who values (or pays for) this kind of stuff.
>
> I think you are pretty brave for posting your 'baby.' I have been
> holding
> my breath because
> I thought it might provoke a lot of disagreement or outright
> disparagement
> of your effort. At
> this point I don't know enough to say if what you have posted is
> altogether
> technically accurate but
> I always check 'free' advice anyway.
>
> You are correct, I think, in the way some people approach books. I am
> struggling to understand
> some of the features in Oracle and have quite an extensive library of
> Oracle
> books. Most of them
> I haven't read cover to cover. I tend to read them a chapter, or even a
> paragraph at a time depending
> on what my issue is. I download a lot of papers, "how-too's", tips and
> tricks.
>
> The value of the books on the market to me is to answer the bigger
> questions
> of why and when (or how much)
> instead of what and how. Its always helpful to me when somebody says,
> "On an
> OLTP system is should be X and
> on a DS system it should be Y." It gives me a point at which to start
> looking. The oracle books usually
> provide the exact syntax describing how a feature or function is
> implemented
> but don't answer the question,
> for me, "Is this an appropriate thing to do in a small datawarehouse
> environment..." I know, "It depends."
>
> So, thanks for posting!
>
> Don Freeman
> Oracle 9i OCP
>
>
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
> [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Juan Cachito Reyes
> Pacheco
> Sent: Thursday, February 26, 2004 9:05 AM
> To: oracle-l_at_freelists.org
> Subject: Re: Your opinion please :) explanation of my point of view
>
>
> Thanks for your opinion.
>
> Now if you think "kill lazy and bad dbas", I can't do too much about
> this.
> I think every one likes his job, and a paper like this can wake up his
> interest in reading to a bad dba, and help to introduce a good dba who
> is
> starting to read.
>
> Yes this is true, the idea is to introduce to all this people to
> tunning.
> I think if every one would read the Oracle document as they should, 50%
> of
> the book would be useless. If you take randomly a good tunning book and
> seek
> the same in Oracle tunning documentation, 90% is in the Oracle
> documentation, at least!!
>
> But even when you read and got an OCP, you need some guide about what
> you should check first, better and simple explanations, for example
> about
> CURSOR_SPACE_FOR_TIME there is not a clear explanation about when to
> use
> them.
> You need a guide that introduce to tunning. to make you understand what
> is
> important and what is the most important.
>
>
> ----- Original Message -----
> From: "Igor Neyman" <ineyman_at_perceptron.com>
> To: <oracle-l_at_freelists.org>
> Sent: Thursday, February 26, 2004 9:53 AM
> Subject: RE: Your opinion please :) explanation of my point of view
>
>
> > If "newbie DBA" doesn't like to read, he/she'd better be in different
> > business...
> >
> > Igor Neyman, OCP DBA
> > ineyman_at_perceptron.com
> >
> >
> >
> > -----Original Message-----
> > From: oracle-l-bounce_at_freelists.org
> > [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Juan Cachito Reyes
> > Pacheco
> > Sent: Thursday, February 26, 2004 7:48 AM
> > To: oracle-l_at_freelists.org
> > Subject: Re: Your opinion please :) explanation of my point of view
> >
> > Thanks for your opinion, tellme what do you think, about this.
> >
> > Point by point
> > 1) About the set of checklist, I agree, but the goal is to introduce
> to
> > tunning, in the market there are several excellent tunning books,
> > (including
> > the documentation where is almost all), but people don't read them.
> > I decided something short, a checklist explaining very very briefly
> what
> > you
> > can tune, the most important, the first steps, for newbies, now if you
> > want
> > more information, you can go to documentation.
> > For example about statistics, I had two pages of a BRIEF explanation,
> > but no
> > body is going to read all that, because instead of 8 pages it will be
> 60
> > pages, it will be preferable to read the documentation, but several
> > questions you should had read some moment, shows people don't like to
> > read,
> > people who never took the time to read neither concept manual, so I
> > decided
> > to explain the most important, briefly.
> >
> > For example, about statistics, the explanation is very short
> > 1.1 Statistics
> > The optimizer works based on statistics, if they are old, or
> inaccurate
> > you'
> > ll get a wrong execution plan.
> >
> > You must recalculate statistics every time an important change had
> > happened
> > in it:
> >
> > . Periodically, based on normal changes in a database
> >
> > . After importing a big amount of data
> >
> > . When distinct values in primary columns change
> >
> > . After creating indexes and table
> >
> > 1.1.1 Test database
> > If this is the first time you get statistics, you must remember some
> > database has fixed execution plans, or any other consideration can
> cause
> > a
> > statistics recalculation cause serious problems, as general rule do it
> > first
> > in ha test database, before doing in the production database.
> >
> > 1.1.2 Recalculating statistics
> > Oracle recommends DON'T USE ANALYZE to gather statistics, the package
> > USE
> > DBMS_STATS, this package get more statistics, specially for new
> > features.
> >
> > Don't execute DBMS_STATS on SYS schema.
> >
> > This command has dozens of options, like parallel execution, etc. etc.
> > you
> > must read them.
> >
> > To gather all statistics
> >
> > EXEC DBMS_STATS.GATHER_DATABASE_STATS();
> >
> > To gather statistics in a schema:
> >
> > EXEC DBMS_UTILITY.ANALYZE_SCHEMA('ADM','COMPUTE');
> >
> > To gather statistics in a schema, more precisely, the one we use,
> > because
> > our database is a small database:
> >
> > EXEC DBMS_STATS.GATHER_SCHEMA_STATS( OWNNAME=>'ADM',
> > ESTIMATE_PERCENT=>100,METHOD_OPT=>'FOR ALL COLUMNS SIZE SKEWONLY');
> >
> >
> > What you understand after this is
> > -optimizer needs statistics
> > -changing statistics can cause you problems, first use a test database
> > -use dbms_stats not analyze
> > That's all, and I think this is the basic thing you have to
> understand,
> > I
> > know dbas (not ocps) who don't know that simple fact," they have to
> > recalculate statistics periodically". Because their database are small
> > and
> > comparing with sql server it takes a similar amount of time to
> process,
> > they
> > don't see it as a problem or a mistake.
> >
> > 2)About the optimizer_index_caching I read a lot, because we have a
> > problem,
> > we solved setting this parameter, about this parameter I say:
> > "This parameter sets the possibility to find blocks accessed through
> an
> > index in memory.
> >
> > Default value is 0, 0 means that no one block accessed through index
> > will be
> > found in memory THIS IS FALSE. A value of 90% is advisable"
> >
> > Could you giveme an example how could I explain it better.
> >
> > 3) About
> > "but pays no attention to individual business processes (or indeed
> > development modules)."
> > Could you giveme an example what for example I could add ,
> > But I'm not explaining in this paper things like ORDERED hint, because
> > for a
> > newbie, first he have to do the basic things, once he had done all of
> > them,
> > if he continue having problems, then the correct way is to read a more
> > serious document.
> > Because if you give advanced points, he will try them first, is like
> > special
> > hints, I think you heard about them, they are not in documentation
> > because
> > it could cause problems to new dbas, because they could try to use
> them
> > to
> > solve problem, when the reality is they can be used only
> exceptionally.
> > but
> > there are book out there once you get the enough experience you could
> > buy
> > them.
> >
> > Now if you want another point of view, or a better idea about this,
> you
> > are
> > welcome :).
> >
> > ----- Original Message -----
> > From: "Niall Litchfield" <n-litchfield_at_audit-commission.gov.uk>
> > To: <oracle-l_at_freelists.org>
> > Sent: Wednesday, February 25, 2004 7:29 PM
> > Subject: RE: Your opinion please :)
> >
> >
> > hi
> >
> > I have to admit I don't like the paper much. it looks like a set of
> > checklists with little or no reasoning behind them. for example the
> > suggestions on optimizer_index_caching have just start at x and work
> > from
> > there. where x is apparently an arbitrary number.
> >
> > my deeper problem is that the article seems to suggest that it is
> > possible
> > to tune systems but pays no attention to individual business processes
> > (or
> > indeed development modules). I disagree, the logical unit for tuning
> is
> > the
> > thing that runs badly, the logical time to do it is when writing the
> > code
> > for it. setting db wide parameters is sticking plaster on the titanic.
> > perhaps.
> >
> > Niall
> >
> > -----Original Message-----
> > From: AC.GWIA.oracle-l_at_freelists.org
> > [mailto:AC.GWIA.oracle-l_at_freelists.org]
> > Sent: Wed 25/02/2004 18:41
> > To: jreyes_at_dazasoftware.com; oracle-l_at_freelists.org
> > Cc:
> > Subject: Your opinion please :)
> >
> >
> >
> > Hi I took sometime to do a paper, to help newbies in tunning, this is
> > not to
> > become they expert, but at least they know there are statistics in the
> > database
> >
> > If you get some time, and give some opinion about it, like the
> previous
> > mistake I did with IN function, you are welcome.
> > Or something important I'm missing (for newbies dbas of course).
> > Did you remember the first time you had a tunning problem, before the
> > ocp,
> > and you didn't knew where to start to check,and lost long time,
> changing
> > some database parameter to see if that improved something, the idea is
> > to
> > save that step.
> >
> >
> >
> http://www.geocities.com/juancarlosreyesp/101basictunningonOracle9i.pdf
> >
> > Juan Carlos Reyes Pacheco
> > OCP
> >
> >
> > ----------------------------------------------------------------
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