what should be the course of action in case of Dual FMC failure in Boeing 737 ng
No one has stated to blindingly soddin obvious....
Cycle the FMC CB's and keep your fingers crossed.
Dual FMC fail is a known issue. A Static Ram Fault in the failing FMC can flood the intersystem bus with garbled data. This causes the offside FMC to fall over when the data handler gets overloaded.
"All things being equal, the simplest solution tends to be the right one"