  We present a theoretical investigation of the origin of Raman-like and
fluorescencelike (FL) features of resonant inelastic x-ray scattering (RIXS)
spectra. Using a combination of local-density approximation + dynamical
mean-field theory and a configuration interaction solver for Anderson impurity
model, we calculate the $L$-edge RIXS and x-ray absorption spectra of
high-valence transition-metal oxides LaCuO$_3$ and NaCuO$_2$. We analyze in
detail the behavior of the FL feature and show how it is connected to the
details of electronic and crystal structure. On the studied compounds we
demonstrate how material details determine whether the electron-hole continuum
can be excited in the $L$-edge RIXS process.
