Solution : https://service.sap.com/sap/support/notes/1024700 (SAP Service marketplace login required)
Key words : 
patches -> sap netweaver -> sap netweaver -> sap netweaver 04 -> entry, lang=en_us&source=swg-ibmjavaisvyou, shorten gc pause times-xconcurrentlevel6controls, starting concurrent gc work-xsoftrefthreshold0controls, unlimited strength jurisdiction policy files, concurrent gc accurate triggering, create anymore threads due, /webapp/iwm/web/prelogin, background helper threads participate, softreferences survive-xconmeter2instructive parameter
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