  Applying the system of linear partial differential equations derived from the
Mellin-Barnes representation and the Miller transformation, we present the
GKZ-system of the Feynman integral of the 2-loop self energy diagram with 4
propagators. The codimension of the derived GKZ-system equals the number of
independent dimensionless ratios among the external momentum squared and
virtual mass squared. In total 536 hypergeometric functions are obtained in the
neighborhoods of the origin and infinity, in which 30 linearly independent
hypergeometric functions whose convergent regions have nonempty intersection
constitute a fundamental solution system in a proper subset of the whole
parameter space.
