  Mesons comprising a beauty quark and a strange quark can oscillate between
particle (B0s) and antiparticle (B0sbar) flavour eigenstates, with a frequency
given by the mass difference between heavy and light mass eigenstates, deltams.
Here we present a measurement of deltams using B0s2DsPi decays produced in
proton-proton collisions collected with the LHCb detector at the Large Hadron
Collider. This measurement improves upon the current deltams precision by a
factor of two. The oscillation frequency is found to be deltams = 17.7683 +-
0.0051 +- 0.0032 ps-1 where the first uncertainty is statistical and the second
systematic. We combine this result with previous LHCb measurements to determine
deltams = 17.7656 +- 0.0057 ps-1.
