RE: Impact of QAQQINI setting IGNORE_DERIVED_INDEX=*YES

We're at V5R4.




                                                                           
             "Bruce Barrett"                                               
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             10/02/2006 12:56                                      Subject 
             PM                        RE: Impact of QAQQINI setting       
                                       IGNORE_DERIVED_INDEX=*YES           
                                                                           
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What version of the O/S are you running?  On V5R3 I loaded PTF MF38886
to correct the solution of the engine choice.
We had a SQL statement running 204 seconds before this PTF and 3 to 4
seconds after.

Bruce Barrett

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-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of darren@xxxxxxxxx
Sent: Monday, October 02, 2006 7:08 AM
To: midrange-l
Subject: Impact of QAQQINI setting IGNORE_DERIVED_INDEX=*YES


I recently did a little fancy footwork with the QAQQINI file so that I
could temporarily set the IGNORE_DERIVED_INDEX setting to *YES.  This
was
necessary to cause IBM's enhanced query engine (SQE) to be used where I
had
derived logicals built against a physical file, and I wanted to do some
SQE
only functions.  My question is, what if I make this
IGNORE_DERIVED_INDEX
*YES permanent.  I was initially afraid of bad query performance, but
through some experiments, it seems rare that the query optimizer ever
picks
a "derived index" type logical anyway.

I guess, my more specific question is, under what conditions will the
query
optimizer pick a "derived index" since my initial experiments show it
not
picking it, despite constructing a logical that should have chosen the
derived index.

The bulk of the offending logicals are DDS built for our BPCS ERP
system.
They are often used to control soft-deleted records.

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