Re: Structure of logical file for query

Tomasz,

I think that the easiest way would be running your SQL statement thru the
Visual Explain (VE) component of the iSeries Navigator. There, you can see
where your query spends most of its time and, at the same time, can use the
index advisor to help you define (and create) the indexes more efficient
four your query.

That said, there are some redbooks that you could check on IBM's
site (although some of them can be somewhat complex).

The guys at Centerfield Technologies ( www.centerfieldtechnology.com) have
some nice presentations and papers (PDF) on their web site, that are worth
getting a look into.

Wishing you (and all my fellow midrangers!) all the best this 2010,

Regards,

Luis Rodriguez
IBM Certified Systems Expert -- eServer i5 iSeries


2010/1/4 Tomasz Skorża <t.skorza@xxxxxxxxxxx>

Hi and happy New Year for everybody :-)

I would like to ask you how you create keyed fields for logical file for
get the fastest "access".

I have such query

Select F1, F2, F3
From File1
Where
F4, F5, F6
Group By F1, F2, F3
Order by F1, F2, F3

I looking in many web pages but everywhere description of creating LF is
general - "Logicals are important to improve performance"

But what should be an order of keyed fields?

What if query change to:

Select F1, F2, F3
From File1
Where
F4, F5, F6
Group By F7, F8, F9
Order by F9, F8, F7

Which statement are most important? Probably "WHERE" ... but order
should be F4/F5/F6 or other (F6/F5/F4)?

Do you remember a web pages where it is described exactly?

--
Pozdrawiam

---------------------------------------------------------
Tomasz Skorża


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