Hi Xiaojun,
One thing that I noticed is that you're using JTA for the first datasource -- but not for the second. I would try having both use JTA and seeing if that fixes the problem you're seeing -- especially if the datasource (java:comp/env/jdbc/testDS1) is referring to the same database (jdbc:mysql://192.168.89.199:3306/jbpm_db).
Regards,
Marco