We classify four families of Levi-flat sets which are defined by quadratic
polynomials and invariant under certain linear holomorphic symplectic maps.
The normalization of Levi-flat real analytic sets is studied through the t
echnique of Segre varieties. The main purpose of this paper is to apply the
Levi-flat sets to the study of convergence of Birkhoff's normalization for
holomorphic symplectic maps. We also establish some relationships between
Levi-flat invariant sets and first-integrals or meromorphic eigenfunctions
of such maps. The results obtained for holomorphic symplectic maps are also
applicable to holomorphic Hamiltonian systems via time-one maps.