Help needed with snmptrapd options

Hi,
	We use snmptrapd binary in our product, and I changed on of the
options i.e. -p which takes the path name, to store the pid 
	of snmptrapd, to something other than /tmp. Could someone tell
me why is this PID of snmptrapd stored in this file.
The problem occurs when I change the path from something other than
/tmp, so is this mandatory to keep this file in /tmp and if yes, why??


Amit  Yadav