Hi, What is the exact enqueue event?. you could possibly look at dba_hist_seg_stat for the sample interval and identify the segment with high enqueue and then query dab_hist_sqlstat for the SQL's containing the table for the DML for the same sample interval. best regards sriram kumar On Thu, Jan 24, 2013 at 8:43 AM, Vasu <vasudevanr@xxxxxxxxx> wrote: > 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 > > > -- > //www.freelists.org/webpage/oracle-l > > > -- //www.freelists.org/webpage/oracle-l