Hi, PTF’s or Program Temporary Fixes are IBM’s way of issuing updates and you should not disregard them or you may find unpredictable things happening with your OS.
You can go to a IBM website to check the required PTF’s and download them too, and it is worth checking with your other software suppliers if they have issues with the OS upgrade.
Also carefully read the documentation supplied with the upgrade and PTF’s for the steps to be taken with the process.
Having said that, an upgrade is not so frightening as it used to be, and after you have taken a full backup of your system V IMPORTANT ! it is just a case of feeding the CD’s in at the prompted times.