Re: Encoded Vector Indexes

["David Morris" <dmorris@xxxxxxxxxxxxx>]

Russell,

Have you run this in debug and analyzed the performance messages?  Also, have 
you 
gone through the optimization section of the SQL programming guide?  Have you 
experimented with query options file (qaqqini) changes?  I would explore those 
options 
before building indexes.

In some cases an EVI will help a slow SQL statement.  Others have had better 
results, but 
a 25% is about the best I have ever seen with an EVI.  The biggest improvements 
usually 
come from normal indexes or by restructuring the statement.  On highly 
normalized files, the 
structure of the statement can really change performance.  For example, 
changing the primary 
file, the source file for key fields, and intermediary joins, can all have a 
big impact on performance.  
Some other tricks are to build indexes over all selected fields if only a few 
are used. This last 
one works best with things like customer name, customer number on a large 
customer file.

David Morris



>>> rconerly@netdoor.com 01/30/01 04:16PM >>>
I have been doing some studying on Encoded Vector Indexes with SQL.  I've been
looking at improving performance of an SQLRPGLE program running on V4R4 
that is using some rather
large files.  The documentation I have found has been limited IMO.

Have any of you experimented with/used EVI's?  And if so, what are the 
pros/cons to using
them?  Does the optimizer inform you that it is using the EVI?  Do you use 
the index
in your select statement or is the index implied?  Please advise.

Thank you in advance.

Regards,
Russell Conerly
Artaban Solutions, Inc.


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