Applying Service Pack 3 in SQL 2012 in Windows 2012 R2
Do I need to remove the possible owner node in cluster while applying SQL Service Pack 3 in SQL 2012 in Windows 2012 R2 .


I suppose you are referring to This support article. The purpose of this support article is if you are trying to install Service pack on cluster without disturbing the current cluster configuration(active nodes) and you want to keep things online.

I suggest take application downtime and apply service pack in that case you don't have to remove any possible owners from the list. I always consider this better way of applying SP, although MS provides you way to update the passive node of cluster without disturbing active node.

This article also helps you when you add node to cluster with RTM version while cluster is on higher SP level, then you have to apply SP on passive node in that case after adding node make sure the added node is not in possible owner list and go ahead and apply patch on passive nodes added so as to make it identical to all nodes.