Hi , I am using the following query to find out the idle time of a user session .

,to_char(logon_time, 'mm/dd/yy hh24:mi:ss') logon_time
-- idle time
-- days separately
,substr('0'||trunc(last_call_et/86400),-2,2) || ':' ||
-- hours
substr('0'||trunc(mod(last_call_et,86400)/3600),-2,2) || ':' ||
-- minutes
substr('0'||trunc(mod(mod(last_call_et,86400),3600)/60),-2,2) || ':' ||
substr('0'||mod(mod(mod(last_call_et,86400),3600),60),-2,2) idle_time
FROM v$session s, v$process p
WHERE s.username IS NOT NULL
-- use outer join to show sniped sessions in
-- v$session that don't have an OS process
AND p.addr(+) = s.paddr
idle_time desc;

My question is whether my query is right? I am using last_call_et column to find the idle time . also if a session is not executing any sql statement then its last_call_et will be reset to 0 and starts update . right?