Re: Switching to Java on OS/400 - got a few questions. -- JAVA400-L

David Morris wrote:

Thorbjørn,

We have used an Apache-based Tomcat release on the iSeries for a few years now. 
That application was written in RPGIV and rewritten in Java -- business logic 
and all. We have a couple of hundred users and a substantial transaction load. 
The database that supports this application has several key tables with +100 
million rows. Performance on an 825 is good and the users like it a lot better 
than the green screen applications it replaced. The speed of your network is 
also a much bigger factor in any web-based application than it is with a green 
screen application.

Do you have a lot of database access? If so, do you use the nativedriver and do you have any measurements of how well it works as opposedto the JTOpen driver?

The speed of the network is relevant because you generally transfer muchmore data per web page than per character screen, but I don't expect thedifference between an OS/400 based and a Linux/Whatever-based server tobe that great. Am I right there?

I have done a lot of benchmarking and we get much better performance running 
natively on the iSeries than on a Windows box. In some cases, I have had to 
adapt code to avoid problematic code. IBM may have been able to help in those 
cases but we do not have software support and I was able to find a work around 
fairly quickly.

Could you briefly list what kinds of problems you have encounted? Iwould expect somethings that are not quite like the Unix/Windows worldthat Java expects.

I would write code differently if I were building a multi-tier application. I 
would cache aggressively and use more stored procedures. That would add some 
complexity but would be required to get similar performance.

When you say multi-tier, does that mean a scenario where data has tomove between JVM's on seperate machines? I.e. over the network?

That is always expensive. But you would move logic in the databaselayer - with stored procedures - in order to accomplish what exactly?

We develop on a workstation and deploy to the iSeries. We have a development, 
test and production environment on the iSeries. The development environment is 
seldom used except for deployment testing, benchmarking and troubleshooting 
iSeries specific issues. We have strict seperation of duties and deploy using a 
hands-off process. Restarting is much slower on the iSeries (about a minute) 
but still acceptable.

So you see the same restart period as I do. Nice to know that. Is itevery time or just a "recompile once" penalty?


Oh, what is the development environment you have?   Curious to know :)

Thanks for your reply.