Purpose of .vmoptions files

In your JDownloader install directory you might see a file called "JDownloader2.vmoptions"

This file is used to define the Java VM parameters for JDownloader.
Every line contains one VM parameter.
Lines starting with # are comments (= ignored).
Most of all times you would want to use it to increase the max. memory.

1. Remove all -Xms and -Xmx lines if existent.
2. Add a new line e.g. -Xmx2g (for 2GB max) or -Xmx1000m (for 1000MB max)

When starting JDownloader again you should see your defined -Xmx value in:
Help -> About JDownloader -> Memory -> See "Max:"
Screenshot:

You can find more Information about Java VM parameters here but only change other parameters than the ones mentioned in this article if you know what you're doing!