History of enq: TX – row lock contention

As a DBA, we should be able to provide the history of locks to the application team to check.

This is the query to get the information from v$active_session_history

This view is part of diagnosis pack, make sure that you have a license for Diagnostic Pack before running this query.

Lock History information – v$active_session_history:
====================================================
col SAMPLE_TIME for a30
col BLOCKING_PATH format a40
set lines 170
SELECT
level,
sample_time,
session_id blocked_sid,
CONNECT_BY_ROOT blocking_session ultimate_blocker_sid,
sys_connect_by_path(blocking_session,’/’)|| ‘/’ || session_id blocking_path
FROM
(– Blocked Sessions
SELECT
s.session_id,
s.blocking_session,
s.sample_time
FROM v$active_session_history s
–s.dbid = 70854992
— AND s.instance_number = 1
–AND s.snap_id BETWEEN 62234 and 62235
WHERE s.blocking_session IS NOT NULL
AND s.event IN
(‘enq: TX – row lock contention’)
UNION
— Blocking Sessions
SELECT s.session_id,
s.blocking_session,
s.sample_time
FROM v$active_session_history s
— s.dbid = 70854992
–AND s.instance_number = 1
–AND s.snap_id BETWEEN 62234 and 62235
WHERE s.blocking_session IS NULL
AND s.event IN
(‘enq: TX – row lock contention’
,’enq: TM – contention’
,’enq: UL – contention’
,’enq: TX – allocate ITL entry’)
AND EXISTS
(SELECT ‘exists’
FROM v$active_session_history bs
–bs.dbid = 70854992
–AND bs.instance_number = 1
–AND bs.snap_id BETWEEN 62234 and 62235
WHERE bs.blocking_session = s.session_id
AND bs.sample_time = s.sample_time
AND bs.blocking_session IS NOT NULL
AND bs.event IN
(‘enq: TX – row lock contention’)
)
)
CONNECT BY NOCYCLE PRIOR session_id = blocking_session
AND PRIOR sample_time = sample_time
ORDER BY sample_time;

What we can do, if the required information not found in v$active_session_history?

Don’t worry, we can get it from dba_hist_active_sess_history view.

Lock History information – dba_hist_active_sess_history:
========================================================

SELECT
level,
sample_time,
session_id blocked_sid,
CONNECT_BY_ROOT blocking_session ultimate_blocker_sid,
sys_connect_by_path(blocking_session,’/’)|| ‘/’ || session_id blocking_path
FROM
(– Blocked Sessions
SELECT
s.session_id,
s.blocking_session,
s.sample_time
FROM dba_active_sess_history s
— WHERE s.dbid = 70854992
— AND s.instance_number = 1
WHERE s.snap_id BETWEEN ‘&StSnap’ and ‘&EdSnap’
AND s.blocking_session IS NOT NULL
AND s.event IN
(‘enq: TX – row lock contention’
,’enq: TM – contention’
,’enq: UL – contention’
,’enq: TX – allocate ITL entry’)
UNION
— Blocking Sessions
SELECT s.session_id,
s.blocking_session,
s.sample_time
FROM dba_active_sess_history s
— s.dbid = 70854992
— s.instance_number = 1
WHERE s.snap_id BETWEEN ‘&StSnap’ and ‘&EdSnap’
AND s.blocking_session IS NULL
AND s.event IN
(‘enq: TX – row lock contention’
,’enq: TM – contention’
,’enq: UL – contention’
,’enq: TX – allocate ITL entry’)
AND EXISTS
(SELECT ‘exists’
FROM DBA_HIST_ACTIVE_SESS_HISTORY bs
— bs.dbid = 70854992
— bs.instance_number = 1
WHERE bs.snap_id BETWEEN ‘&StSnap’ and ‘&EdSnap’
AND bs.blocking_session = s.session_id
AND bs.sample_time = s.sample_time
AND bs.blocking_session IS NOT NULL
AND bs.event IN
(‘enq: TX – row lock contention’
,’enq: TM – contention’
,’enq: UL – contention’
,’enq: TX – allocate ITL entry’)
)
)
CONNECT BY NOCYCLE PRIOR session_id = blocking_session
AND PRIOR sample_time = sample_time

ORDER BY level DESC, blocked_sid, sample_time;

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