KNPC_ANQ_AWAITNONEMPTYQUEUE WAITS ON ADVANCED REPLICATION PUSH (Doc ID 953713.1)

Last updated on MAY 11, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 9.2.0.1 to 11.2.0.2 [Release 9.2 to 11.2]
Information in this document applies to any platform.

Symptoms

While monitoring the database performance , we observe high values for wait events  on knpc_anq_AwaitNonemptyQueue.

These event can be observed on Enterprise Manager or checking wait event views:

-- Observe sid for sessions running push:

column dblink format a30
select /*+ ORDERED */ j.job, j.sid, d.dblink,
SUBSTR(TO_CHAR(J.THIS_DATE,'MM/DD/RRRR HH24:MI:SS'),1,20) START_DATE
from defschedule d, dba_jobs_running j
where j.job in (select job from dba_jobs
where upper(what) like '%DBMS_DEFER_SYS.PUSH%')
and j.job = d.job;


-- Check current wait event

select s.sid, s.serial#, s.event, s.username
from v$session s
where s.sid = <sid> and wait_time=0;


-- Check latest waits on v$session_history

SELECT ash.session_id,
  ash.event_count, ash_total.total_count,
  ash.event_count*100/ash_total.total_count percentage,
  'YES' busy,
  ash.event
FROM (SELECT SESSION_ID,
  SESSION_SERIAL#,
  EVENT,
  COUNT(sample_time) AS EVENT_COUNT
  FROM v$active_session_history
  WHERE sample_time > sysdate - 30/24/60
  AND SESSION_ID = <SID>
  GROUP BY session_id, session_serial#, event) ash,
  (SELECT COUNT(DISTINCT sample_time) AS TOTAL_COUNT
  FROM v$active_session_history
WHERE sample_time > sysdate - 30/24/60
AND SESSION_ID = <SID>) ash_total
ORDER BY percentage;

 

Cause

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