Clause 4 in ISO 9001:2015 and AS9100 Rev D

Answer:
Much of clause 4 is new to ISO 9001 and was not present in the ISO 9001:2008 version. in particular:
4.1 is about understanding the organisation and its context. This requires you to determine what internal and external issues affect your QMS and is new.
4.2 is about understanding the needs and expectations of interested parties. This requires you to identify the parties interested in your QMS and what their needs and expectations are, and is also new.
4.3 is about the scope of the QMS and while this is not new it does require you to consider the scope with the knowledge from 4.1 & 4.2; so a review of the scope is a good idea.
4.4 is about understanding the processes in the QMS. This is very similar to the previous version with the addition of a few things such as addressing the risks and opportunities for the processes.

While 4.1 & 4.2 do not require you to keep documented i nformation it is a good idea to keep your listing of issues, interested parties and their needs so that you can review it for updates as time goes on. A procedure on how you accomplish this might also be needed so that everyone understands how you intend to perform these review.