Upgrade from Plex 5.5 to 7.2.1

Document ID : KB000075542
Last Modified Date : 02/04/2018
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We are planning the migration of our models from 5.5 and 6.1 to 7.2.1. The models are working with C++/RPG and Java/RPG. 
From the documentation I read I know that I have to rebuild and gen the C++ portion with VS 2013 and the Java portion with JDK 1.8. I understood that I don't need to regenerate RPG right? 
What I don't know is the dispatcher or listener that is installed in the IBM i. Do I need to install the one that comes with Plex 7.2.1 and it is backward compatible or am I going to have 2 listeners to communicate with the IBM i?
In the Plex documentation, please review the following link. 


In the link there is the following section. 

RPG Functions Upgrade Requirements 
You do not need to regenerate or rebuild existing RPG functions when upgrading to CA Plex r7.2.1. 

Additional clarification:  
Plex WinC/WinNTC functions are mandatory to regen/rebuild due to compiler changes. System-I Plex RPG objects are not mandatory to rebuild. 
To upgrade to Plex r7.2.1, you need to install Plex r7.2.1 dispatcher on IBM-i and new dispatcher will work fine with existing RPG built objects. 
And make sure you have Plex r7.2.1 client runtime (WinC/WinNTC) installed at Plex client application side.