Performace tunning Queries

TO FIND LONG RUNNING QUERIES:-

select distinct a.sid,a.serial#,a.logon_time,a.username,a.sql_id,a.sql_exec_start,sysdate,a.status,
substr(to_char(NUMTODSINTERVAL(a.sql_exec_start-sysdate, 'day')),5,15) duration ,a.event,a.program,a.module,b.sql_text
from gv$session a, gv$sql b
where a.status='ACTIVE'
and a.username not in ('SYS','SYSTEM')
and b.sql_id=a.sql_id
and b.parsing_schema_name=a.username
and a.program not like 'orac%'
and b.parsing_schema_id=a.user#
order by a.sql_exec_start;


TO CHECK ACTIVE SESSION:-

select * from dba_hist_wr_control


select * from v$active_session_history where sql_id='dt6d6zsrdjsxm' order by sql_exec_start desc

select min(sample_time)
,max(sample_time)
from v$active_session_history

select * from dba_hist_active_sess_history


TO TAKE EXPLAIN PLAN IN DIFFERENT WAYS:-

select * from table(dbms_xplan.display_awr('dt6d6zsrdjsxm'))


select * from dba_users where user_id=195




select * from
dba_hist_Active_Sess_history
where
sample_time BETWEEN  to_date('12-SEP-2017 12:00:56','DD-MON-YYYY HH24:MI:SS')
and  to_date('12-SEP-2017 12:04:56','DD-MON-YYYY HH24:MI:SS')
and user_id=195
ORDER BY sql_exec_start dESC


select * from dba_hist_sqltext where sql_id='993m5xvjsq9dk'