Actually I tried to set the max_connections count to 400 in the first place. But this led to errors on the JBoss stating that the pool could not be filled. So I increased it to 800 which worked fine. (At least for the startup of JBoss. And the preparation phase of the benchmark.) The overall thread count of the database node is about 560 when running the benchmark. Which is 60 threads more than in the idle state. This is the case even when I set the thread_cache_size to 2000. I think that I am not using the /3GB option. I don't even know what you mean by it ;) But actually I monitored for memory paging errors and RAM utilization and there is no problem. In addition as I mentioned before GlassFish had no problems with this configuration. So I think that the interaction of JBoss, MySQL and Windows are causing the problem. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4224486#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...