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
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