Hi, is it really guaranteed, also under very heavy load, that a client has exclusive access to a statefull session bean? Or might it be a problem to use ArrayLists as local variables in a method of a stateless session bean? I use a stateless session bean in the context of a container managed transaction. The bean itself does not require transactions. The bean methods just compute some functions. Under very heavy load (ca. 30.000 transaction / hour), the bean sometimes produces non reproducable wrong function results (ca. 1 / hour). The function results are stored in ArrayLists in the method. Might this be a problem? Thanks, Claudia View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3970047#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...