I need to install a new IBM WAS fixpack in my environment, but my question is if I have to do some special configurations in the Portal or only install the FP? Is a cluster with 3 nodes. My products are:
Most WAS fixpack updates shouldn't require changes to your Portal configuration. However I believe from WAS 8.5.5 fixpack 14, Java 7 is no longer supported. It's a fairly big change and may require you to make some modifications to your environment.
You should also check Portal system requirements: https://support.hcltechsw.com/csm?id=kb_article&sysparm_article=KB0089871#prerequisites
I would suggest applying the WAS fixpack to a test environment and verifying your system is working as expected before applying in your production environment.