When upgrading to the same release you should follow the instructions
"Replacing Licensed Internal Code and IBM i of the same version and
This was initially created for people upgrading from V5R4M0 to V5R4M5 or
6.1.0 to 6.1.1. It could also be applicable to those upgrading from beta
code to current code. Or those upgrading from one resave to another (if
you just really wanted to do it this way).
The steps there are suggesting a 'Manual' IPL and whatnot.
I did notice those steps leave out any LPP's. Which, if your goal is to
get all PTF's is not going to make you happy if you're missing a PTF for
5770ST1 for example.
There's a possible check - DSPPTF 5770ST1.