Hi Nicolas Thx for your quick answer. Ok, i forgot some informations: Using : Java6.0.45 X64 (same problems using Java 7 X64) No, i don't use listeners. I tried with up to 10Gig without success. My (reduced) workflow is : 1) <code> kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); kbuilder.add(ResourceFactory.newClassPathResource(RULES_PATH, getClass()), ResourceType.DRL); kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase.addKnowledgePackages(kbuilder.getKnowledgePackages()); </code> 2) <code> StatefulKnowledgeSession ruleSession = kbase.newStatefulKnowledgeSession(); </code> so far so good 3) insert two supporter objects in session 4) add two more worker objects in session 5) fire all rules 6) read and retract all expected objects 7) dispose session Processing Steps 2)-7) (in a loop with different worker objects, to produce load, so there is always only one session active) work fine for a view times (3-9) then the mentioned exception occurs. I also tried it with 10gig for the jvm but in either test the memoryload does not exceed 3gig. With a reduced rules file size (to < 500k; removed some rules, to test this) i can handle 300000(!) loops without any exceptions. Hope this infos will help. Regards Peter ------------------------------ If you reply to this email, your message will be added to the discussion below: http://drools.46999.n3.nabble.com/Drools-5-5-Problems-with-big-rules-file... To start a new topic under Drools: User forum, email ml-node+s46999n47000h33(a)n3.nabble.com To unsubscribe from Drools, click here<http://drools.46999.n3.nabble.com/template/NamlServlet.jtp?macro=... . NAML<http://drools.46999.n3.nabble.com/template/NamlServlet.jtp?macro=...