Apache batik memory issues

Hello All,


Recently I have started using Apache Batik to create PDF files from SVG 
templates. The application is used to generate exam pages for students. 
It works great but it uses a huge amount of memory. This is sometimes 
annoying because i have to increase the memory limit to over 4Gb to have 
it complete the task. There are in general lots of students (500+) and 
in one case 2000+ students. This will, of course, eat memory like an 
elephant I accept that.

I want to reduce this memory footprint and have found one issue in my 
program where I need help with.

I am using the Java JRE 1.6.0_32, Batik 1.7 and PDFBox 1.6.0.

The program has the following flow:

1.    fetch students from source (Excel file)
2.    create workers to generate pdf from svg
3.    while not all students have been processed do
3.1      replace information in svg document ( using w3c functions from 
Document class  ) (this is done by worker)
3.2      generate PDF from svg document (Using PDFTranscoder)
3.3      check if there are more students; true: goto 3.1; false: 
continue with step 4
4.   clean up workers
5.   generate single pdf from all generated pdfs using PDFBox
6.   done

It is a multi threaded environment and all the workers are in their own 
thread, each worker has a copy of the svg document, they dont share 
anything (for obvious reasons).

What I have found  is what comes after step 4, after cleaning up the 
workers I am still using 1Gb of memory which is much more than when I 
start (around 128Mb). I suspect there is some caching here and there but 
I have not enough knowledge from batik to fix this problem.

Who can help me or has the answer for me?


Thanks in advance,

Hilbert Mostert