Re: Index Advisor question

[Vernon Hamberg <vhamberg@xxxxxxxxxxxxxxx>]

Statistics are things like a histogram of buckets (up to 256, IIRC) of 
values and frequent values. They are used to help the optimizer make 
better decisions, not based on the old assumptions that were pretty static.

So the index may not be used for selectivity so much as generating these 
statistics. This is all part of the new query engine.

HTH
Vern

On 6/11/2013 3:00 PM, Mike Cunningham wrote:
> Does anyone know what it means when the Index Advisor shows "Source for statistics" as the Reason Advised? This site http://pic.dhe.ibm.com/infocenter/iseries/v7r1m0/index.jsp does not show that as a valid value for the column.  We are getting this on 7 of our top 10 "most expensive" advised indexes. When we look at the existing indexes the index the advisor thinks should be created already exists.
>
>
> And part two..... is there an easy way to find indexes that exist but are not used very often?  Index Advisor does a great job of telling me ones that should be created but I think we have existing ones that never get used and just add overhead
>
> Thanks
>
>
> Mike Cunningham
> Pennsylvania College of Technology