How to monitor Long Running Sql statements

This script is to find out long running sql statement in database. It is also returning values 0,1 and 2 to use with Nagios monitoring tools to show normal,warning, critical alerts.


set long 5000
set pages 1000
select  case when max_sql_time is null then 0
    when max_sql_time < 1800 then 0
    when max_sql_time between 1800 and 3600 then 1
    else 2 end
    as return_code, 'OpName is : ' || opname||
    '. The max long running SQL in v$session_longops ran for '|| max_sql_time ||
    ' seconds. Message is ' || message ||
    '. Username is ' || l.username ||
    '. OSuser is ' || sess.osuser||   
    '. Program is '|| sess.program ||
    '. Machine is ' || sess.machine ||
    '. SQL Text is ' || s.sql_fulltext
    as return_statement
    from (select max(elapsed_seconds)
          as max_sql_time,
          username,
          opname,
          message,
          sql_address
          from v$session_longops
          where
           last_update_time > sysdate - interval '15' minute
          and message not like 'RMAN: aggregate input: backup%'
          and message not like 'RMAN: aggregate output: backup%'
          and message not like 'RMAN: incremental datafile backup%'
         group by username, opname, message,sql_address) l,v$sql s,v$session sess
        where l.sql_address=s.address
         AND  sess.sql_address=s.address
       UNION ALL
SELECT 0 as return_code ,to_clob('There are no rows returned') as return_statement   from dual