We study the nonlinear dynamics of a complex system, described by a two-dim
ensional reversible map. The phase space of this map exhibits elements typi
cal of Hamiltonian systems (stability islands) as well as of dissipative sy
stems (attractor). Due to the interaction between the stability islands and
the attractor, the transition to chaos in this system occurs through the c
ollapse of the stability island and stochastization of the limiting-cycles
orbits. We show how to apply the method of discrete parametric control to s
tabilize unstable high-period orbits. To achieve highly efficient control w
e introduce the concepts of local and global control. These concepts are us
eful in situations where there are "dangerous" points on the target orbit,
i.e., the points where the probability of breakdown of control is high. As
a result, the dangerous points turn out to be much more sensitive to extern
al noise than other points on the orbit, and only the dangerous points dete
rmine how effective the control is.