ASH report - missing blocking session info
- From: Vasu <vasudevanr@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Wed, 23 Jan 2013 21:13:22 -0600
We have had perf-issues in our 11.2.0.3, Rac DB a while ago. As a
post-mortem started looking into DBA_HIST_ACTIVE_SESS_HISTORY and ASH
report for that period.
The scenario is : A session on instance-1 was blocked by a session from
instance-2 (blocker) for nearly 40 minutes,
For the blocked session on instance-1, dba_hist_active_sess_history has
300+ records, a record for every 30 sec approximately ,
with all records having the same info : Waiting on enq wait, with blocking
sesssion info :sid,serial# ,instance and status GLOBAL. (which is OK).
Wow..I thought I was making a good progress, only a record away from the
culprit.. but the blocker info is missing in DBA_HIST_ACTIVE_SESS_HISTORY,
and ash report too . :(
Quick glance of the 1st article thru google said 'only active sessions are
sampled'.. so is it possible the blocker was idle after some DMLs (without
issuing a commit)?
OR has any one come across 'missing session info ' for valid cases or
possibly a bug?
Thanks
Vasu
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