  We investigate the influence of domain walls on the vortex dynamics in
superconductors with multi-component order parameters. We show that, due to
their complex structure domain walls can carry vortices with fractional flux
quanta. The decay of conventional vortices into fractional ones on domain walls
is examined. This decay presents an extraordinarily strong pinning mechanism
for vortices and turns domain walls occupied with pinned fractional vortices
into efficient barriers for the vortex motion. Therefore, domain walls can act
as fences for the flux flow, preventing the decay of the remnant magnetic flux
enclosed by them. Furthermore, the consequences of this property of domain
walls on the vortex dynamics are discussed in connection with observed noise in
the hysteresis cycle, using the Bean model of the critical vortex state. Based
on this picture experimental data in the unconventional superconductors
UPt$_3$, U$_{1-x}$Th$_x$Be$_{13}$ and Sr$_2$RuO$_4$ are interpreted.

Superconductivity;Strongly Correlated Electrons