  On the (1+3) dimensional Minkowski spacetime, for small, regular initial
data, it is well-known that the Dirac-Klein-Gordon system admits a global
solution. In the present paper, we aim to establish the uniform boundedness of
the total energy of the solution for this system. The proof relies on
Klainerman's vector field and Alinhac's ghost weight methods.
  The main difficulty originates from the slow decay nature of the Dirac and
wave components in three space dimensions. To overcome the difficulty, a sharp
understanding of the structure for this system, and a new weighted conformal
energy estimate are required. In addition, we also provide a few scattering
results for the system.
