How to quantify memory activity?

    1. Total amount of active virtual memory: total demand for memory
    2. paging rate: proportion of memory actively used

How to determine the amount of swap space in use:
 BSD:    % pstat -s
                   110224K allocated + 13556k reserved = 123780k used,
                      16300k available
 ATT:    % swap -l
                    swapfile                    dev      swapl     blocks        free
                    /dev/dsk/c0t0d0s1    32,1       16        164400      162960

             %  sar -r   5
                    17:58:52    freemem   freeswap
                    17:58:57            361       179616