stat meanings of computing nodes

I submitted a job to a Linux cluster which uses SGE job scheduler. The job stat is qw for a long time, so I inspected the stats of computing nodes using "qstat -f". I found that many nodes were labelled with stats "d", "adu" and "E". I wonder what these stats mean. The Grid Engine Man pages listed these stats for filtering queue instances ( -qs {a|c|d|o|s|u|A|C|D|E|S} ), but no further explanation on the meaning of these stats. What do the states mean?