I'm addressing the list from the most recommendations down. This
particular one, the only EVI recommended, has been recommended over
600000
times (since day 1).
I've only recently been building indexes based on the advisor's
recommendations.
The advisor also lists the estimated time spent as a result of not having
the index. This can be an insightful field to look at as well, as
sometimes an index recommended much fewer times has a much larger impact
when created because the time shown amounts to minutes per recommendation
while the one recommended more times only shows a fraction of a second
each.
I never could find an IBM published way of measuring the fields in tandem,
but I figured that I cared much more about a user waiting for 30 seconds
as opposed to waiting for a fraction of a second, no matter how many times
the fraction of a second was being experienced. This seemed to be
validated by users, though I will have to say that I never have had a user
come up and say: "Wow, it's faster". I've always had to solicit
feedback, and I had to count "Yes, that screen has been faster the last
couple of days..." as the pinnacle of success from a user standpoint. :-)
Because the logicals you create will also need to be removed if someone
else wants to modify the physical file, I also recommend coming up with a
naming convention so that you know when you can just blow them away. It
helps to know when you can delete logicals because they are there for
performance purposes, and when you're going to cause a program to fall in
a heap because it isn't there...
Andrew Lopez
Systems Analyst
Phone: 803-714-2037
Email: ALopez@xxxxxxxxxx
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