We are seeing OOME's in Jenkins when parsing large Fitnesse results files (35mb). For example:

Reading results as US-ASCII from /.../fitnesse-result.xml
Parsing results...
java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOf(Arrays.java:2882)
at java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.java:100)
at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:515)
at java.lang.StringBuffer.append(StringBuffer.java:306)
at com.sun.org.apache.xalan.internal.xsltc.runtime.StringValueHandler.characters(StringValueHandler.java:49)
at com.sun.org.apache.xml.internal.utils.FastStringBuffer.sendSAXcharacters(FastStringBuffer.java:998)
at com.sun.org.apache.xml.internal.dtm.ref.sax2dtm.SAX2DTM2.dispatchCharactersEvents(SAX2DTM2.java:3068)
at com.sun.org.apache.xalan.internal.xsltc.dom.SAXImpl.characters(SAXImpl.java:1562)
at com.sun.org.apache.xalan.internal.xsltc.dom.DOMAdapter.characters(DOMAdapter.java:330)
at GregorSamsa.template$dot$2()
at GregorSamsa.applyTemplates()
at GregorSamsa.template$dot$0()
at GregorSamsa.applyTemplates()
at GregorSamsa.applyTemplates()
at GregorSamsa.transform()
at com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet.transform(AbstractTranslet.java:603)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:709)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:313)
at hudson.plugins.fitnesse.NativePageCountsParser.transformRawResults(NativePageCountsParser.java:25)
at hudson.plugins.fitnesse.NativePageCountsParser.parse(NativePageCountsParser.java:17)
at hudson.plugins.fitnesse.FitnesseResultsRecorder.getResults(FitnesseResultsRecorder.java:131)
at hudson.plugins.fitnesse.FitnesseResultsRecorder.getResults(FitnesseResultsRecorder.java:109)
at hudson.plugins.fitnesse.FitnesseResultsRecorder.perform(FitnesseResultsRecorder.java:73)
at hudson.tasks.BuildStepMonitor$3.perform(BuildStepMonitor.java:36)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:705)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:680)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:658)
at hudson.model.Build$RunnerImpl.post2(Build.java:161)
at hudson.model.AbstractBuild$AbstractRunner.post(AbstractBuild.java:627)
at hudson.model.Run.run(Run.java:1400)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
Build step 'Publish Fitnesse results report' changed build result to FAILURE
Build step 'Publish Fitnesse results report' marked build as failure

I'm fairly certain this OOME is due to memory usage by this parsing since we don't see OOME at any other time, and there is plenty of memory usually available according to our monitoring.