• Subject: Re: SQL order by question
  • From: DAsmussen@xxxxxxx
  • Date: Thu, 21 Jan 1999 13:58:54 EST

Gary,

In a message dated 1/21/99 9:32:00 AM Eastern Standard Time,
Gary_Lehman@mail.mchcp.org writes:

> Forgive me for sounding sort of ignorant, but when you say build the access
>  paths do you just mean rebuilding the logicals?  If so, if you build them
in
>  order of least used to used the manager knows this?

Yes, the manager knows in what order the logicals were built and searches the
first n (someone posted the new figure a while back, I don't recall) of them
in date order before deciding to build its own.  This brings up an interesting
question that perhaps someone listening in at IBM could answer.  Why?  Oh, I
understand the original logic -- a well-designed database shouldn't have that
darned many logicals to search in the first place.  Those of us trying to run
third-party packages (e.g., BPCS ships with over 30 logicals against the
inventory transaction history file, most of which are _USELESS_ for anything
other than MRP) have rarely seen a well-designed database.

With access path evaluation taking so little time in comparison to building a
new access path over a large file, why not remove the access path
consideration restriction or at least provide a system value?  I too am a
proponent of specifying the physical file in an SQL statement, but this can
cause problems in tuning should you recompile a logical for performance and
then have the aforementioned n logicals recompiled for a different reason.
Programs that once ran well suddenly start dying, and nobody knows why because
the guy/girl that recompiled the original logical for performance didn't
document it adequately and has since taken that $30K signing bonus to work
somewhere else.  With the advent of data warehousing, client/server, and
terabyte storage capabilities, why do we still have this antiquated access
path evaluation restriction?

Curious,

Dean Asmussen
Enterprise Systems Consulting, Inc.
Fuquay-Varina, NC  USA
E-Mail:  DAsmussen@aol.com

"Success is not the result of spontaneous combustion.  You must first set
yourself on fire." -- Fred Shero
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