DA40 Diamond Star
Flight Crew Commercial; Flight Crew Flight Instructor; Flight Crew Instrument; Flight Crew Multiengine
Situational Awareness; Human-Machine Interface
ATC Issue All Types; Conflict NMAC
Flight Crew Requested ATC Assistance / Clarification
Human Factors; Aircraft
We were in a hold over SAC VOR at about 3;000 ft. with flight following from North Cal. Another aircraft (CE-172?) came within 300 ft. vertical separation (according to my Stratus 3 and ForeFlight display on iPad). The pilot of the other aircraft involved in this encounter (CE-172?) also reported to North Cal that his ForeFlight warned of being close to our aircraft. That day there were a lot of aircraft in the area (according to Stratus 3 and Foreflight display).
Pilot reported a NMAC with a Cessna while holding over the Sacramento VOR.