  Oscillations in the B0_s - anti-B0_s system were studied in events selected
from about 4.3 million hadronic Z^0 decays registered by DELPHI between 1992
and 2000. This paper presents updates of two published analyses ([11,12]). The
first analysis, which utilizes leptons emitted with large momentum transverse
to a jet, was improved by means of a better algorithm for the vertex
reconstuction and a new algorithm for flavour-tagging at production time. The
second analysis, which utilizes D_s-lepton events, was improved by optimizing
the treatment of proper time resolution. No signal of B0_s oscillations was
observed and limits on the mass difference between the physical B0_s states
were obtained to be:
  \Delta m_s > 8.0 ps^{-1} at the 95% C.L. with a sensitivity of \Delta m_s =
9.1 ps^{-1} in the high p_t lepton analysis and \Delta m_s > 4.9 ps^{-1} at the
95% C.L. with a sensitivity of \Delta m_s = 8.6 ps^{-1} in the D_s-lepton
analysis. Previously published results on these analyses are superseed. The
combination of these results with those obtained in other independent analyses
previously performed in DELPHI (D_s-hadron, exclusive B0_s, inclusive vertex)
gives: \Delta m_s > 8.5 ps^{-1} at the 95% C.L. with a sensitivity of \Delta
m_s = 12.0 ps^{-1}.
