Cognos 10.2.1 moving from User Based Licencing to PVU Licencing

[marella]

We are moving from our User based licencing to PVU Model Licencing.
Currently we have 5 Application Servers (disptachers) and out of that one we are going to dedicate for PVU Users.
What are the steps to make this change smooth? as All 5 Servers currently dedicated for Cognos only and have Cognos installed in those servers.

I know that we need to change the core size to 2 from 4 on that particualar server which is going to used for PVU Users, what else we need to make sure.
Any other changes needed?