RE: New System Development Tomcat Tuning

Buck,

I must have missed your post but I would like to review your system
that forces an upgrade to run an identical application with WAS over
green screen. That has not been my experience at all, I could see
needing to add memory, but that is about it. There are  quite a few
techniques that can be employed to address performance issues.
One real big one is resource caching and pooling - the Apache
Commons project has something that might get you started. Another
is to make sure you are using native access. Also, you need to make
sure you are competing on an even basis with existing interactive
workload and have compiled all of your Jars and classes to
optimize 40. It also easy to rely too heavily on synchronization.

I get great performance from Tomcat. I can't tell that servlet based
JSP applications are any slower than green screen. On a 730 with
a CPW of 560/560, we get < .5 second response in either environment.
It runs at an average of 60% utilization through the day taken at 30
minute
intervals. When I run similar code on a 270 with a CPW of 150, I still
get <
1 second response, where WebSphere ran about 4 (that was with the
1.2 JDK, and 3.5.2 - things may have improved).

As far as the learning curve of Servlets, it is similar in my opinion
to
learning CGI and all of its intricacies. It takes us about 3 months to
get
a programmer real comfortable with the servlet environment we use.

David Morris

>>> Buck.Calabro@commsoft.net 05/10/02 08:49AM >>>
>I am going to develop a new application on
>the AS400 v5r1. I want to keep my business
>logic completely in RPGLE using DB2/400
>as the database. My problem is that I
>need browser based screens and I am not
>able to decide whether I should use Java
>or CGI to handle browser requests.

One question you need to answer is: will the same iSeries be running
green-screen applications at the same time it will be serving
servlets?
Think of the cost to buy iSeries hardware that will run WebSphere AND
have
sufficient interactive features to continue the green screen
applications.

I posted a question last week regarding real experience with replacing
a
thick client with a browser based client and go no responses except
for
vendors trying to help out.  I may be in a peculiar situation working
for a
software vendor, but we are having difficulty convincing potential
customers
to spend money to upgrade a 720 to a new 820 with L2 cache.  IBM says
that
WAS requires L2 cache to run well and I believe them.

Don't think that Tomcat will be a cheap alternative.  I found no more
than a
15% difference in performance between WAS 3.5.4 and Tomcat on a 620,
and
maybe 10% on an 820 running WAS 4.0.2 and Tomcat.  (Tomcat is a bit
faster)
Basically, Tomcat needs the same hardware that WAS does.  This may turn
out
to be a tuning issue (which can be addressed in another thread).

Do consider the cost of upgrading your iSeries in the calculation of
what
technology to employ.
  --buck