Blocking Sessions and Locked Objects Scripts!

June 11, 2019   Performance Tuning

How to find historical blocking session and lock with below scripts. Change date time column which is specified with bold character.

select v.sql_text,v.sql_fulltext,sub.* from v$sql v,
(select sample_time,s.sql_id sql_id, session_state, blocking_session,
owner||'.'||object_name||':'||nvl(subobject_name,'-') obj_name,s.program,s.module,s.machine
from dba_hist_active_sess_history s, dba_objects o
where sample_time between
to_date('27/02/2019 07:30:02','DD/MM/YYYY HH24:MI:SS')
and
to_date('28/02/2019 15:10:02','DD/MM/YYYY HH24:MI:SS')
and event = 'enq: TX - row lock contention'
and o.data_object_id = s.current_obj#
order by 1 desc) sub where sub.sql_id=v.sql_id;

How find momentarily blocking session and lock with below scripts.

select s1.username || '@' || s1.machine
|| ' ( THIS SID=' || s1.sid || ' )  is blocking '
|| s2.username || '@' || s2.machine || ' ( SID=' || s2.sid || ' ) ' AS blocking_status
from gv$lock l1, gv$session s1, gv$lock l2, gv$session s2
where s1.sid=l1.sid and s2.sid=l2.sid
and l1.BLOCK=1 and l2.request > 0
and l1.id1 = l2.id1
and l2.id2 = l2.id2 ;


How to generate Kill script of Blocking sessions.

SELECT
'alter system kill session ''' || SID || ',' || s.serial# || ',@'||inst_id||''';',sid,username,serial#,process,NVL (sql_id, 0),
sql_address,blocking_session,wait_class,event,p1,p2,p3,seconds_in_wait
FROM gv$session s WHERE blocking_session_status = 'VALID'
OR sid IN (SELECT blocking_session
FROM gv$session WHERE blocking_session_status = 'VALID');


query result will be like below if you have blocking session in your database.

alter system kill session '4,45390,@1';
alter system kill session '5,5636,@2';
alter system kill session '6,78324,@3';


If application developers or client offers you to kill any session or sessions group like SQL Net Client, or JDBC Client sessions or RMAN sessions.

You need to find session SID and SERIAL# with below script.

select s.SID,s.SERIAL#,S.USERNAME from v$session s where s.sid=63;


You can kill any session with its SID and SERIAL# number like below.

alter system kill session '55,2543';


Customer offers you to kill sessions group like SQL Net Client, or JDBC Client sessions or RMAN sessions. You can generate kill session script like below. You can change event to kill any other event group sessions.

SELECT 'kill -9 ' || p.spid, s.username,
'alter system kill session ''' || SID || ',' || s.serial# || ''';'
FROM v$session s, v$process p
WHERE s.paddr = p.addr(+)
AND s.SID IN (SELECT SID
FROM v$session_wait
WHERE event LIKE 'SQL*Net message from client%')
and s.username ='DEVECI'
and s.saddr not in ( select SES_ADDR from v$transaction );


If you have just SQL_ID and you need to find sessions related with this SQL_ID, then you can find like below and you can generate kill script like below.

SELECT 'kill -9 ' || p.spid, s.username,
'alter system kill session ''' || SID || ',' || s.serial# ||',@'||p.inst_id|| ''';'
FROM gv$session s, gv$process p
where s.SQL_ID like '4p5w3j8b3yhcw'
and s.PADDR = p.ADDR (+)
and s.STATUS='ACTIVE'
order by 1;


How can kill RMAN sessions which gives extra efor to the database like below.

SELECT 'kill -9 ' || p.spid, s.username,
       'alter system kill session ''' || SID || ',' || s.serial# ||',@'||p.inst_id|| ''';'
  FROM gv$session s, gv$process p
 WHERE s.paddr = p.addr(+)
and s.TYPE ='USER'
and s.program like 'rman%';


If you want to kill all users sessions except Application user. You can use following query to do this task.

SELECT 'kill -9 ' || p.spid, s.username,
       'alter system kill session ''' || SID || ',' || s.serial# ||',@'||p.inst_id|| ''';'
  FROM gv$session s, gv$process p
 WHERE s.paddr = p.addr(+)
and s.TYPE ='USER'
AND s.USERNAME <>'MSDEVECI';

 
How to kill some users sessions which is still executing more than 300 seconds, then you can use following useful Oracle DBA script.

SELECT 'kill -9 ' || p.spid, s.username,
       'alter system kill session ''' || SID || ',' || s.serial# || ''';'
  FROM v$session s, v$process p
 WHERE s.paddr = p.addr(+)
       AND s.SID IN (
   select sid
  from v$sql_monitor where status ='EXECUTING'  and elapsed_time/1000000> 300
  and username in ('MEHMET','SALIH'))


How to kill some users sessions which are still executing more than 720 seconds and without SYS user and User type ( not background sessions ), then you can use following useful Oracle DBA script.


SELECT
'alter system kill session ''' || SID || ',' || s.serial# ||',@'||p.inst_id|| ''';'
FROM gv$session s, gv$process p
WHERE s.paddr = p.addr(+)
and s.TYPE ='USER' and s.username!='SYS' and status='ACTIVE' and last_call_et > 720;