Just select your light, in Parameter's, Shadow Type (I use Raytraced), & do the same for all your lighting, for best results view in Iray, to see what you'll get in the finished render, once your finished with your lighting you can go back to whichever settings you use while building your scene, you can even run your rendering in that setting, & still have the finished render in Iray, which will help keep things under control, VRAM wise, also use
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, 'Cutaway' will remove anything outside of the camera view, while keeping your lighting as is, the only things it doesn't touch are HDRI's. The Screenshot is from Perspective view, rather than the camera, of my latest Render post.
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