hi kukeltje, very appreciate your replies! I'm a new one here. And I even don't know JIRA... What a pity! I go through the topic you have metioned http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4238433#... If I don't misunderstand that post, changing org.hibernate.dialect can get my problem solved? However, my org.hibernate.dialect is configured as org.hibernate.dialect.MySQLInnoDBDialect... <property name="hibernate.dialect">org.hibernate.dialect.MySQLInnoDBDialect</property> | <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> | <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/jbpm4db</property> | <property name="hibernate.connection.username">root</property> | <property name="hibernate.connection.password">123456</property> | <property name="hibernate.hbm2ddl.auto">update</property> | <property name="hibernate.show.sql">true</property> | | <mapping resource="jbpm.repository.hbm.xml" /> | <mapping resource="jbpm.execution.hbm.xml" /> | <mapping resource="jbpm.history.hbm.xml" /> | <mapping resource="jbpm.task.hbm.xml" /> | <mapping resource="jbpm.jpdl.hbm.xml" /> | <mapping resource="jbpm.identity.hbm.xml" /> So I think my problem is different from that. ? And the ConstraintViolationException here is because `FK_EXEC_SUPEREXEC` but not `FK_EXEC_INSTANCE` (Yes, it's due to that I use sub-process. Because if I put these 2 fork flows into One process, one embedded into another, tasks in Inner-Fork-Flow will be created twice) This time I try to be clever to USE SOME KIND OF SEARCH FUNCTIONALITY (I was stupid enough yesterday~~). I learn Google! hahaha Fortunately, I find this issue list https://jira.jboss.org/jira/secure/BrowseVersion.jspa?id=10052&versio... (And I know JIRA! Fortunately again) And I find this issue JBPM-2303 UNRESOLVED Exception with a process containing a fork/join You can touch it:https://jira.jboss.org/jira/browse/JBPM-2303 I ran that tests and got exceptions. I think join/fork flow has its own bugs. I should go to see what happens in jBPM4. I should have enough time to do that. It's my fault. I really want to know what's wrong with my code, What is the actual reason caused that exception happens. If it is proved to be a bug, I can sleep well tonight~~ hahaha Please help me again. Thx! Or I have to wait for jBPM4 released? hahahaha My e-mail: crazydog.eric(a)gmail.com View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4238661#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...