Re: Calling java from RPG - how to increase performance

    Hi Larry,

    I'm not a fan of RPG to Java calls.  When interprocess communication is
necessary, I normally use asynchronous messaging.  It avoids a lot of
overhead and typically improves throughput.

    In this case, if you were starting from scratch, I'd suggest all Java,
primarily for the standards-based XML capabilities.  Since you already have
a ( working? ) set in RPG, in the interest of time I would probably use RPG
for everything, with embedded SQL.  It sounds as though you have a lot
invested already.

> > into SQL insert statements. These are then executed over
> > the database on the iSeries. To do this I utilise the Java
> > Native Interface (JNI) to create and use java objects.

> > C) Run the whole process in java - I could execute the SQL using JDBC.
> > (but would that just be even slower???)

    I don't understand these two statements taken together; aren't you using
JDBC already?

    As of V5R2, if the program runs any length of time, runtime compilation
is recommended over CRTJVAPGM.


                                                         Joe Sam

Joe Sam Shirah -        http://www.conceptgo.com
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----- Original Message ----- 
From: "Aaron Bartell" <albartell@xxxxxxxxx>
To: "Java Programming on and around the iSeries / AS400"
<java400-l@xxxxxxxxxxxx>
Sent: Wednesday, May 18, 2005 5:18 PM
Subject: Re: Calling java from RPG - how to increase performance


> Why do you even have RPG in the mix?  Java has much better
> capabilities in the realms of XML, XSLT, and SQL.  I would reconsider
> my architecture before I tried to get RPG to Java performance better.
> Or just take RPG all the way through.
>
>
> I have written a handful of RPG to Java pieces (ie
> http://mowyourlawn.com/html/RPGMail.php) and each time I can never get
> enterprise ready performance out of it.  IMO, RPG to Java is not yet
> ready for prime time.  Java to RPG on the other hand performs quite
> well (at least when you have the Java running in a more cached
> environment than that of OS/400 -  Tomcat for instance).
>
> Those are my thoughts,
> Aaron Bartell
>
> On 5/18/05, Larry Ducie <Larry_Ducie@xxxxxxxxxxx> wrote:
> > Hi chaps,
> >
> > I posted the following on the RPG forum and got a couple of responses,
but I
> > was advised to fire it at you chaps for more info. As a result of the
> > responses on the RPG forum I'm now using jt400Native.jar instead of
> > jt400.jar to get a little extra oomph, but I'm still not sure if I've
set
> > the JVM up with the right values to optimise my application - basically,
I'm
> > looking for some advice on what inputOpts I should set when starting the
JVM
> > using JNI. I'm not even sure what options there are! I'm even starting
to
> > question the idea of using JNI at all, as I'm not sure what overhead
each
> > RPG-to-Java call actually adds. It seems almost impossible to get any
> > banchmarks for this stuff. Any help on this would be most welcome.
> >
> > Anyway, here's the post...
> >
> > Hi,
> >
> > I have written a RPG service program that transforms XML [using
transform
> > stylesheets (XSLT)] into SQL insert statements. These are then executed
over
> > the database on the iSeries.
> >
> > To do this I utilise the Java Native Interface (JNI) to create and use
java
> > objects. Basically, I create a transformer object. I then pass the
object an
> > XML stream source to transform, and a stream result to hold the
transformed
> > data.
> >
> > For each transformation (assuming the transformer object does not
change) I
> > have to create a new StreamSource object:
> >
> > To create the stream source object from RPG I have to perform the
following
> > steps:
> >
> > 1) Create a String object from the XML file path. (RPG-to-Java)
> > 2) Create a File object from the String. (RPG-to-Java)
> > 3) Free the String object - no longer needed. (RPG-to-Java)
> > 4) Create a StreamSource object from the File object. (RPG-to-Java)
> > 5) Free the File object - no longer needed. (RPG-to-Java)
> >
> > I create a StreamResult object for each job that runs this process, so I
> > only perfrom the following once:
> >
> > 1) Create a String object from the result file path. (RPG-to-Java)
> > 2) Create a File object from the String. (RPG-to-Java)
> > 3) Free the String object - no longer needed. (RPG-to-Java)
> > 4) Create a StreamResult object from the File object. (RPG-to-Java)
> > 5) Free the File object - no longer needed. (RPG-to-Java)
> >
> > Now, this all works fine - I'm just not sure it's running as fast as it
> > could be - approx 0.2 seconds for each transformation. After a few
hundred
> > transformations it seems to slow down - could this be the Garbage
Collector?
> > I start the JVM manually using JNI (with version 1.4.2 set). I also set
the
> > classpath manually (using putenv). The XML file path is retrieved from a
> > data queue, and the result file path is created by the program. All RPG
> > object references are freed one-at-a-time, not by pushing/popping the
local
> > frame.
> >
> > So, what are the best ways to speed things up???
> >
> > I've considered the following:
> > A) Create a custom java class that performs the conversions from file
path
> > to StreamSource/StreamResult and just call it with the two byte arrays.
> > B) Allocate more memory to the JVM - what's the best size? What's the
> > default size?
> > C) Run the whole process in java - I could execute the SQL using JDBC.
(but
> > would that just be even slower???)
> > D) I've not compiled the XML jar files (Xerces.jar, Xalan.jar, etc)
because
> > I believe the JIT compilers are better than CRTJVAPGM. Is this true?
> > E) I've not copied and compiled jt400.jar to put in my classpath -
should I
> > need to?
> >
> > Basically, does the JNI carry a large overhead? Should I minimise the
number
> > of RPG-to-Java calls by writing a custom class? Should I optimise the
java
> > environment by allocating memory or compiling objects? I need your wise
> > words.
> >
> > The program source is available if it helps. (We're running at V5R2M0)
> >
> > Thanks
> >
> > Larry Ducie
> > --