I don't know if anyone replied yet, but I will try and answer this.
Depending on your unix flavor, the nice values will be different. Linux
nice values are between -20 (highest priority) and 19 (lowest priority),
with a default of 0. For hpux, the values are from 0 to 39, with a default
of 20.
I have used nice for Unidata on HPUX many times and never had any problem.
Renice is the command to change nice level. Use man renice to get help on
the command. While using renice command just make sure to use correct pid
for the process.
Another command you may want to have a look is kill
