Oracle 12c in-memory option
It's still in beta.  It won't be released till the 12.1.0.2 patchset.  As such, unless you're in the beta program, not much information is available yet.

I think the NDA has been lifted, as I saw Tom Kyte speak about it at Collaborate 14 in Las Vegas a couple of weeks ago, but, you can't actually use it yet.

Hope that helps.