Find The Maximum run time of a concurrent request in a 

particular day using FND History Table :

select DESCRIPTION, request_id, request_date, phase_code, status_code, requested_start_date, 
actual_start_date, actual_completion_date,ROUND(((nvl(actual_completion_date,sysdate) -actual_start_date) * 1440)/60,2)   "Runtime (in hours)"  ,
argument_text from apps.fnd_conc_req_history 
where 
DESCRIPTION in ('&program_name')
and actual_start_date between to_date('21-04-2015 00:00:00','DD-MM-YYYY HH24:MI:SS')
and to_date('22-04-2015 23:59:59','DD-MM-YYYY HH24:MI:SS')
order by request_date desc


Note : Change the Actual start date and to_date based on your requirement