Specifically, why would it help to fix a PermGen OutOfMemoryError issue?

Also, bonus points for an answer that points me to the documentation on JVM arguments...
['https://Stackoverflow.com/questions/12114174', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/242135/']
`-XX:PermSize -XX:MaxPermSize` are used to set size for Permanent Generation. 

Permanent Generation: The Permanent Generation is where class files are kept. These are the result of compiled classes and JSP pages. If this space is full, it triggers a Full Garbage Collection. If the Full Garbage Collection cannot clean out old unreferenced classes and there is no room left to expand the Permanent Space, an Out‐of‐ Memory error (OOME) is thrown and the JVM will crash.
In Java 8 that parameter is commonly used to print a warning message like this one:

> 
> Java HotSpot(TM) 64-Bit Server VM warning: ignoring option
>  MaxPermSize=512m; support was removed in 8.0
> 
> 
> 

The reason why you get this message in Java 8 is because Permgen has been replaced by Metaspace to address some of PermGen's drawbacks (as you were able to see for yourself, one of those drawbacks is that it had a fixed size).

FYI: an article on Metaspace: <http://java-latte.blogspot.in/2014/03/metaspace-in-java-8.html>