  Let $ \pi $ be an irreducible Harish-Chandra $ (\mathfrak{g}, K) $-module,
and denote its associated variety by $ AV(\pi) $. If $ AV(\pi) $ is reducible,
then each irreducible component must contain codimension one boundary
component. Thus we are interested in the codimension one adjacency of nilpotent
orbits for a symmetric pair $ (G, K) $. We define the notion of orbit graph and
associated graph for $ \pi $, and study its structure for classical symmetric
pairs; number of vertices, edges, connected components, etc. As a result, we
prove that the orbit graph is connecetd for even nilpotent orbits.
  Finally, for indefinite unitary group $ U(p, q) $, we prove that for each
connected component of the orbit graph $ \Gamma_K(O_{\lambda}) $ thus defined,
there is an irreducible Harish-Chandra module $ \pi $ whose associated graph is
exactly equal to the connceted component.
