Re: JT400/JDBC performance issues

["Mark Phippard" <MarkP@xxxxxxxxxxxxxxx>]

It might have been on MIDRANGE-L but I didn't find anything in the 
archives.

What I thought I read was that when you use a View, the Query Optimizer 
does not see some or all of the Indexes on the table and does not take 
them into account.  In some cases, this can yield poorer performance as 
unnecessary temporary tables may need to be created.

As I said, I could be wrong.






Dieter.Bender@xxxxxxxxxxx
Sent by: java400-l-bounces@xxxxxxxxxxxx
02/19/2003 12:10 PM
Please respond to Java Programming on and around the iSeries / AS400 
 
        To:     Java Programming on and around the iSeries / AS400 
<java400-l@xxxxxxxxxxxx>
        cc: 
        Subject:        Re: JT400/JDBC performance issues


Hi Mark,

where did you here this, that might have been true many years ago.
Today there is not any problem using views.

Dieter

Mark Phippard schrieb:
> Dieter,
> 
> >> To get performance that bad it seems like it would
> have to have 
> something
> >> to do with the JDBC statements you are executing.  Are
> you using SQL 
> Views
> >> in your SELECT?  Generally, these perform worse than
> Tables on the 
> iSeries.
> >
> > the diffrence is less than 0,1 sec
> 
> I will admit that I have never measured it and we only
> use Tables in our 
> statements.  I am basing this on statements I have seen
> elsewhere that 
> said when you use a View, the query optimizer is not able
> to take into 
> account the indexes that are over the table and in some
> cases this will 
> yield significantly worse performance.
> 
> Mark
> 
> 
> 
> 
> 
> 
> 
> Dieter.Bender@xxxxxxxxxxx (Dieter Bender)
> Sent by: java400-l-bounces@xxxxxxxxxxxx
> 02/19/2003 04:48 AM
> Please respond to Java Programming on and around the
> iSeries / AS400 
> 
>         To:     Java Programming on and around the
> iSeries / AS400 
> <java400-l@xxxxxxxxxxxx>
>         cc: 
>         Subject:        Re: JT400/JDBC performance
> issues
> 
> 
> Mark,
> 
> On Wednesday 19 February 2003 02:23, you wrote:
> > Suresh,
> >
> > To get performance that bad it seems like it would have
> to have 
> something
> > to do with the JDBC statements you are executing.  Are
> you using SQL 
> Views
> > in your SELECT?  Generally, these perform worse than
> Tables on the 
> iSeries.
> 
> the diffrence is less than 0,1 sec
> 
> >
> > You do not mention how large your tables are or how
> many records you are
> > selecting.
> >
> > Finally, once those issues are worked out, a big area
> where problems 
> will
> > occur with the iSeries is if you do not use Connection
> Pools. 
> Establishing
> > a connection to the iSeries has a high overhead.  Using
> a pool 
> eliminates
> > that problem.  However, we are talking seconds not
> minutes.
> 
> I've made measures on this, normally a connect shoul be <
> 0,3 sec and 
> making 
> 800 connections to a little 270 should not be a problem.
> 
> You should use connection pooling anyway, its easier to
> use for 
> transaction 
> handling and talking about web applications, you never
> know how many users 
> 
> wil connect, but in this case you won't see any
> improvement.
> 
> Dieter
> 
> >
> > Hope this helps,
> >
> > Mark
> >
> >
> > _______________________________________________
> > This is the Java Programming on and around the iSeries
> / AS400 
> (JAVA400-L)
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> 
> -- 
> mfG
> 
> Dieter Bender
> 
> 
> DV-Beratung Dieter Bender
> Wetzlarerstr. 25
> 35435 Wettenberg
> Tel. +49 641 9805855
> Fax +49 641 9805856
> www.bender-dv.de
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> _______________________________________________
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