How to improve 3-D unstructured mesh quality with prism layers?
 

Hi all, my question is related to control of mesh (3D, unstructured) quality after generation of prism layers in ICEM-CFD.
My mesh had lowest “Quality” criterion more than 0.5 but after generation of prism layers it dropped to less than 0.1 even after smoothing. So any suggestion how can I control the quality.
Another similar question: Is it absolutely necessary to make prism layer on all boundaries or is it possible to exclude small oblique walls of geometry to increase the mesh quality without compromising solution stability/accuracy.
For example, if I have the geometry as shown in figure attached is it necessary to make prism layer on part 2?