This software site repository URL,
http://download.eclipse.org/releases/oxygen/
provides access to the software repository for the
Eclipse Oxygen Simultaneous Release.
This repository site URL is typically pre-populated in the list of software repositories when you install the Eclipse Platform or SDK.
For more information about installing or updating software, see the Eclipse Platform Help.
NOTE: Due to structural changes you cannot update from a Mars (or prior) all-in-one package to a Oxygen version. If interested in the technical details, see bug 332989 and bug 490515.
Updating from Neon to Oxygen should work but is not extensively tested for all features.