Yes, a quota is required in order for DFM to report usage data, however if you are not using PM you can use monitoring quota also.
Have added sample monitoring quota.
#QuotaTarget    type                disk    files    thold    sdisk    sfile
#-----------    ----                ----    -----    -----    -----    -----
#Sample of dfm monitoring quota
#*              tree@/vol/nfsvol1    -        -        -        -        -