The biggest benefit for LPARs is that they can be managed online. The CPU, Memory and adapters can be allocated on the spot without downtime, offcourse due care has to be taken. The process is also referred to as DLPAR. DLPAR is nothing but a daemon which runs on server. The name of the process is IBM.drm. Without this DLPAR is not possible, so far as I know.
I searched a video for you demonstrating DLPAR. Its about 10 minutes video which demonstrates how to change LPARs on the fly, on IBM machines using HMC(Hardware Management Console). I hope sure you’ll like it as you watch it.
Dynamic Logical Partitions for changing the LPAR and OS on the fly including CPU, Memory and PCI slots with adapters initially Dedicated CPUs but also shows the differences for Shared CPU LPARs.