select opname, target, to_char(start_time, ‘yyyy-mm-dd hh24:mi:ss‘) start_time, elapsed_seconds elapsed, 
executions execs, buffer_gets/decode(executions, 0, 1, executions) bufgets, module, sql_text
from v$session_longops sl, v$sqlarea sa
where sl.sql_hash_value = sa.hash_value
and upper(substr(module, 1, 4)) <> ‘RMAN‘
and substr(opname, 1, 4 ) <> ‘RMAN‘
and sl.start_time > trunc(sysdate)
order by start_time;

select b.username username,a.disk_reads reads, 
    a.executions exec,a.disk_reads/decode(a.executions,0,1,a.executions) rds_exec_ratio, 
    a.sql_text Statement 
from  v$sqlarea a,dba_users b 
where a.parsing_user_id=b.user_id 
 and a.disk_reads > 100000 
order by a.disk_reads desc;

select sql_text,executions 
from (select sql_text,executions, 
   rank() over 
    (order by executions desc) exec_rank 
   from v$sql) 
where exec_rank <=5;

select disk_reads,sql_text 
from (select sql_text,disk_reads, 
   dense_rank() over 
     (order by disk_reads desc) disk_reads_rank 
   from v$sql) 
where disk_reads_rank <=5;

select buffer_gets,sql_text 
from (select sql_text,buffer_gets, 
   dense_rank() over 
     (order by buffer_gets desc) buffer_gets_rank 
   from v$sql) 
where buffer_gets_rank<=5;