• Subject: Re: Query Performance
  • From: Chuck Lewis <clewis@xxxxxxxxxx>
  • Date: Mon, 13 Sep 1999 13:32:01 +0100

Thanks Scott !

I ran one of the queries under debug and am looking over the information right
now. Never having done this before, there IS some interesting stuff here !

Chuck

Scott Mildenberger wrote:

> You can use CHGQRYA to change QRYTIMLMT to 0 seconds.  This stops the query
> itself from running (you get a message where you can ignore or cancel).  The
> message will contain an estimate from the predictive query governer on how
> long the query will take to run.  If you look in the job log you will see
> info messages on whether the query will need to build indexes or whatever in
> order to run the query.  You can then change the query or build a LF and
> then try running it again to see if the estimated time is reduced.  This
> allows you to experiment with speeding up queries without having to let the
> query run.
>
> By the way, you can set the QRYTIMLMT to some value to not let users run
> queries that the system estimates are going to run a very long time.  There
> is also a system valueQQRYTIMLMT if you want to limit queries system wide.
>
> Scott Mildenberger
>
> > -----Original Message-----
> > From: Chuck Lewis [SMTP:clewis@iquest.net]
> > Sent: Monday, September 13, 1999 3:41 AM
> > To:   MIDRANGE-L@midrange.com
> > Subject:      Re: Query Performance
> >
> > Thanks Guys !
> >
> > I'll try that.
> >
> > Neither of you played around with Predictive Query Governor or ever heard
> > of it ?
> > Know it's been around for awhile but also know that in general it's been
> > one of
> > those "well hidden secrets".
> >
> > Chuck
> >
> >
> > Pete Hall wrote:
> >
> > > At 08:20 09/10/1999 , Chuck Lewis wrote:
> > > >We've got "novice" query users creating queries over a 3rd party
> > > >applications' data base. They do a fairly good job in selection logic
> > > >but have no real knowledge of Logical Files so they are using Physical
> > > >Files which are NOT keyed so I am REALLY questioning the efficiency of
> > > >some of these queries.
> > > >
> > > >I know there is something called the "Predictive Query Governor" - is
> > > >any using this or have you and is it helpful in the above scenario for
> > > >"ratting out" problems ?
> > >
> > > The AS/400 will use the proper access path. You just need to make sure
> > that
> > > it exists. This often means running the most common queries in debug,
> > > examining the job log and creating whatever indexes are needed.
> > >
> > > Pete Hall
> > > pbhall@execpc.com
> > > http://www.execpc.com/~pbhall
> > > +---
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