1. Identify heavy SQL (Get the SQL with heavy BUFFER_GETS)

Select sql_text ,executions ,disk_reads ,buffer_gets

from v$sqlarea
where decode(executions,0,buffer_gets,buffer_gets/executions)
> (select avg(decode(executions,0,buffer_gets,buffer_gets/executions))
+ stddev(decode(executions,0,buffer_gets,buffer_gets/executions))
from v$sqlarea) and parsing_user_id !=3D;