Bigness of the tangent bundle of del Pezzo surfaces and D-simplicity

We consider the question of simplicity a ring $R$ under action its differential operators $D_R$. give examples to show that even when is Gorenstein and has rational singularities need not be simple $D_R$-module; for example, this case homogeneous coordinate smooth cubic surface. Our are rings Fano varieties, our proof proceeds by showing tangent bundle such variety big. also partial converse projective $X$, embedded some multiple canonical divisor, then as $D_R$-module implies $X$ thus singularities.