was it a special resolution or a matter of norm?
A special resolution in regards to McCain. But as far as resolutions go, they are a matter of norm. They issue them for a lot of things - to express the "sense" of the Senate. They don't mean anything legally. As an example here is another one they introduced :
S. RES. 612 Expressing the sense of the Senate that President George W. Bush, President Dmitry Medvedev of the Russian Federation, and other participants in the 2008 Group of Eight (G8) Summit in Toyako, Hokkaido, Japan should work together to foster a more constructive relationship,
Of course this is totally meaningless.