We discuss how the lepton CP phase can be constrained by accelerator andreactor measurements in an era without dedicated experiments for CP violationsearch. To characterize globally the sensitivity to the CP phase \delta_{CP},we introduce a new measure, the CP exclusion fraction, which quantifies whatfraction of the \delta_{CP} space can be excluded at a given input values of\theta_{23} and \delta_{CP}. Using the measure we study the CP sensitivitywhich may be possessed by the accelerator experiments T2K and NOvA. We showthat, if the mass hierarchy is known, T2K and NOvA alone may exclude,respectively, about 50%-60% and 40%-50% of the \delta_{CP} space at 90% CL by10 years running, provided that a considerable fraction of beam time is devotedto the antineutrino run. The synergy between T2K and NOvA is remarkable,leading to the determination of the mass hierarchy through CP sensitivity atthe same CL.