I think, I found an explanation. In fact, the exception is thrown because jbpm try to update two DBs in one transaction without xa-datasources. jbpmDS is updated and the EJBTimerBean (I don't know why !) try to update DefaultDS. In the jmx-console, i have updated the MBean jboss.ejb:service=EJBTimerService,persistencePolicy=database in order to use jboss.jca:service=DataSourceBinding,name=JbpmDS instead of jboss.jca:service=DataSourceBinding,name=DefaultDS I stop then restart the MBean and I was able to activate the 'Evaluate' button. But, i'have still a question. In which file, we configure the DS for the EJB Timer Bean ?? Thanks in advance View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4200527#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...