We probe the nature of steady shear flow of entangled polymer solutions by superimposing either small amplitude oscillatory shear or small step strain and analyzing the resultant mechanic responses. Our results show that (a) polymer dynamics (in terms of stress relaxation) are accelerated relative to the quiescent dynamics in direct proportion to the underlying shear rate and (b) the steady shear is a viscous state where chains are displaced past one another on a time scale of the reciprocal rate, consistent with the idea of convective constraint release.