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Re: PC Memory/Data Bases


  • Subject: Re: PC Memory/Data Bases
  • From: PaulMmn <PaulMmn@xxxxxxxxxxxxx>
  • Date: Mon, 28 Apr 1997 00:44:18 -0400

fixed

At 06:26 PM 4/27/97 -0400, Chris wrote:
>John P. Carr said:
>
>>Well I guess that the PC data bases will handle a Million or more
>records,   
>>Now if only the PC plateform and its memory were stable enough to
>>trust............
>>By the way guys and gals,  How many "memory" errors on the AS/400 do you
>>remember
>>over the last 5 - 10 years ? ? ?   Just curious.    (68ns or were they
>>72ns chips?)
>
>I don't think it necessary here to "preach to the choir" and cover all the
>areas I find the AS/400 far superior to alternate platforms.
>
>But I do think it's important that we keep in mind the usefulness of
>alternate platforms. I'm not saying we all need to be "hype junkies" and
>run off buying whatever the latest glossy ad tells us too. However, if you
>can put several million records and a query tool on a pc on the
>controller's desk, you might save yourself a few days of performance
>tuning.


Welll...  we've let our users use IBM's Query/400 and write their own
queries.  Usually it's not a problem.  However, some of our "Query Experts"
try to do wonderful things in a query.  Including writing queries with 5 or
10 files (I'm NOT kidding!).

You can imagine just how efficient queries of this complexity are.  One such
runs for a couple of hours to create an output file, which is downloaded to
a PC so some database program can massage the data even more for an hour or so.

However, our user got the job done.  And he did it himself, without trying
to pry scarce IS resources free.  And he got it done NOW.

Our resident Query -EXPERT- (a former IS director at one of our divisions,
who knows how to make Query sit up and sing, and who -knows- the data base)
is in the process of revising this process.  So far, he's taken the single
query and turned it into a chain of 20 or 30, each of which does a little
piece of the job and creates assorted output files used later in the
process.  By careful selection of the files he uses, and the data he's
massaging, he's trimmed the time of this thing to less than 15 minutes.
MUCH less.

The point--  the AS/400 does the job that the PC platform does.  Faster.
When used properly.  It's important to have someone who knows the database
and the Query application write or review the project.  This same expert has
performed similar magic for some of our manufacturing locations.

The advantage of downloading a file for use in a query on a PC is that the
user can do the job independent of IS resources.



NB--  Why is it that IBM -still- doesn't optimize the query creation
process?  The routine that searches for suitable access path -still- quits
after 15 files or so.  We have a number of files that hold millions of
records, some of which have over 60 (that's sixty) logical files.  Even when
there's a perfectly good access path, Query won't find it if it's not in the
first 15.  And goes ahead and re-indexes millions of records.

Granted, if you use the name of the logical file instead of the physical
file, you've solved that problem (which is part of what our expert does in
his tuning process).

But when you're talking about such large files, I'd think Query ought to be
smart enough to keep looking for a suitable access path.

Why isn't there an option on the Query command that says, "Search all
available access paths?   {*YES *NO}."  This would at least give us the
option of making that choice.

--Paul E Musselman
PaulMmn@ix.netcom.com


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