Regular measurements of oscillations of the Sun-as-a-star's photosphere have been performed at the Crimean Astrophysical Observatory since 1974. In this experiment, a Babcock solar magnetograph detects Doppler effect difference between the central part and the limb part of the solar disk (using the Fraunhofer absorption line Fe I λ 512.4 nm). Over last 30 years the measurements were made during 1807 days (in aggregate more than 11 thousand hours). The most significant peak of the power spectrum of the line-of-sight velocity variations corresponds to the period P = 159.9655±0.0005 min. The period is in good agreement, within the error limit, with the Stanford value 159.9663±0.0008 min, inferred before from the independent 1977—1994 measurements, which supports strongly solar origin of the period. This oscillation has nearly constant initial phase over the total 30-year interval and reveals substantially non-harmonic mean profiles of both, velocity and radius, perturbations. The true physical nature of the P phenomenon and the source of its excitation are unknown. It is supposed that the periodic oscillation of the Sun's photosphere is caused by superfast rotation of the central solar core.