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Re: Your opinion please :) explanation of my point of view

From: Juan Cachito Reyes Pacheco <jreyes_at_dazasoftware.com>
Date: Thu, 26 Feb 2004 10:05:23 -0400
Message-ID: <01ed01c3fc71$944a7f00$2501a8c0@dazasoftware.com>


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.

> 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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Received on Thu Feb 26 2004 - 08:05:31 CST

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