Re: AS/400 and Java

Dieter, Bruce,  and Mark,

The CRTJVAPGM command is still useful and can dramatically improve
performance even on the latest release. For example, an uncompiled
version of Tomcat and our site takes at least 5 minutes to start w/o
compilation. With compilation it takes less than 2 minutes. I don't
fully
understand why since most classes are loaded by a custom class loader,

but I have seen it enough to know that this is absolutely the case.
This
can be very important when you have a short window to install upgrades,

so I always compile new/changed Jar and Class files that are installed

on our system. I submit these compiles to run during periods of low
activity. I then create symbolic links to those Jar and Class files
in our various application directories. Standalone applications tend to

benefit even more from native compilation.

We use JTOpen 3.2 JT400Native.jar (compiled to 40) loaded with the
system class loader and have not seen any problems. This makes a big
difference in performance. In our case RPG is invoked via triggers and

at the native exit point to swap user/group and performance is good.

David Morris

>>> brucej@MRC-PRODUCTIVITY.COM 11/04/02 01:31PM >>>
<zqRNUXuvxA0b1SvskN2V4Q@public.gmane.org> wrote

> 1. read the recent manuals (Performance Capabilities Reference
> recommends the JIT environment since V4R5!)
> 2. don't use CRTJVAPGM on boxes > V4R5

I stopped using CRTJVAPGM long ago. Everything seems to be OK.

> 3. don't use the native driver, its buggy, use the latest Toolbox
driver

I use the native driver all the time. Everything seems to be OK.

> 4. don't use record level access (more IO Operations compared to
SQL)

 I have not used record level access. Everything seems OK. I primarily
code
interactive applications and SQL seems to be good enough.

> 5. run your application server on inexpensive boxes (Wintel, or Linux
 on
Intel), if possible (scalability)

Linux may offer some hope. My new Intel/win2000 crashes at least once
a
month and they can't fix it.
In 9 years I did see AS400 crash, once.

> 6. Don't mix Java with RPG and/or COBOL, the context change is very
expensive

The context change cost probably is often more than compensated. I have
a
Java application that calls a big RPG program which calls other CL and
RPG
programs and they all do file read/update/delete. The timer shows that
all
these take 100 ms (0.1 second). I time it from getting a connection to
returning a connection. Other applications with fewer file operations
but
exclusive JDBC SQL calls would always take more than 100 ms.

> 7. use all features of the as400 as database server, you've paid for
it.
> 8. for maximal speed with minimal hardware requirements use assembler
 and
shift your bytes bit by bit.

 Labor is more expensive than hardware.

 Bruce





_______________________________________________
This is the Java Programming on and around the iSeries / AS400
(JAVA400-L) mailing list
To post a message email: JAVA400-L@midrange.com
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/cgi-bin/listinfo/java400-l
or email: JAVA400-L-request@midrange.com
Before posting, please take a moment to review the archives
at http://archive.midrange.com/java400-l.