jBPM Process Instance migration not working in 6.1 version

Question

I am trying to migrate jBPM process instances in jBPM 6.1 whereas they doesn't seem to work. here is the logic :

        Boolean t = ksession.execute(new GenericCommand<Boolean>() {
        public Boolean execute(org.kie.internal.command.Context context) {

            KieSession ksession = ((KnowledgeCommandContext) context).getKieSession();

            WorkflowProcessInstanceUpgrader.upgradeProcessInstance(
                ksession,
                migrateProcessRequest.getProcessInstanceIds().get(0),
                "org.test.process1",
                mapping);
           return true;
   }
});

whereas the moment It is out of the execute method the process name and node names are same as the old process has .Also it doe not give any error but in database there is no change in the process instance.

Could anyone please help me with this. Is there anything to be taken care of before calling the execute . What about the User transactions ?

any sort of information would be really helpful. Please answer!!!!!

Thanks