Aaron Donat clarifies Using the Named System Database Feature for Microsoft Dynamics GP 2013. If you’re a partner you should read this.
Using the Named System Database Feature for Microsoft Dynamics GP 2013 – Developing for Dynamics GP – Site Home – MSDN Blogs
SQL & DataMicrosoft & the GP EcosystemGP 2013
Archived post from 2012. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.