  On the Type IIB toroidal T^6 orientifolds with generic flux
compactifications, we conjecture that in generic supsersymmetric Minkowski
vacua, at least one of the flux contributions to the seven-brane and D3-brane
tadpoles is positive if the moduli are stabilized properly, and then the
tadpole cancellation conditions can not be relaxed. To study the
supsersymmetric Minkowski flux vacua, we simplify the fluxes reasonably and
discuss the corresponding superpotential. We show that we can not have
simultaneously the positive real parts of all the moduli and the negative/zero
flux contributions to all the seven-brane and D3-brane tadpoles. Therefore, we
can not construct realistic flux models with the relaxed tadpole cancellation
conditions. When studying the supsersymmetric AdS vacua, we obtain flux models
with the seven-brane and D3-brane tadpole cancellation conditions relaxed
elegantly, and we present a semi-realistic Pati-Salam model as well as its
particle spectrum. The lifting from the AdS vacua to the Minkowski/dS vacua
remains a great challenge in flux model buildings on toroidal orientifolds.
