Yes. The default attribute map is a synchronized hash map because concurrent hash map consumes more memory as the number of the connections grows. You can change the default map by implementing your own IoSessionDataStructureFactory and setting its new instance in IoAcceptor or IoConnector. Hmm, or MINA could provide a concurrent hash map backed implementation out of the box (although it will not be the default). Please let me know if we can decrease the memory consumption with concurrent hash map. That would be the best solution. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4149782#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...