I frequently use to find the process run time by executing the following query:
select prcsinstance seq,
prcstype, prcsname,
begindttm, enddttm,
runstatus sta,
trunc((enddttm - begindttm)*24) HH,
(trunc((enddttm - begindttm)*24*60) - (trunc((enddttm - begindttm)*24)*60)) MM,
(trunc((enddttm - begindttm)*24*60*60) - (trunc((enddttm - begindttm)*24*60))*60) SS
from tablex;

This may also help you.

Tamil