I have two work flow one is approval workflow & another is reassignment workflow in which manager approval is need for reassignment, once manager will approve, task should be reassing to requested user in approval workflow. How can i reassign the task from process 2 to process1. Please suggest.
I haven't tried it for this, but try using a correlation.
Create the correlation in the process you want to notify -> add an event subprocess in that process who's start event is an interrupting Message event that takes a string as input that is the user id you want to reassign it to -> add an Update Task in the event in the event subprocess -> change the Update Task's operation to "Reassign" and assign it to the user id that the notifying processes sends in -> have the notifying process send the notification into this process with the user id you want to reassign the instance to.
In his blog post from about a year ago, Arun Pareek did an infinitely better job of explaining correlations than I have - http://beatechnologies.wordpress.com/2011/10/17/working-with-custom-correlation-in-oracle-bpm-suite-11g-ps4-feature-pack/.