Use plan baseline to stabilize query plan. I use the following two links as reference. http://rnm1978.wordpress.com/2011/06/28/oracle-11g-how-to-force-a-sql_id-to-use-a-plan_hash_value-using-sql-baselines/ http://kerryosborne.oracle-guy.com/2009/04/oracle-11g-sql-plan-management-sql-plan-baselines/ step 1: find the problem query which use bad query plan rather than the good plan. step 2: find the snapshot id which has has the good plan plan for this sql_id. VARIABLE cnt NUMBER EXECUTE :cnt := DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE( - sql_id => '0yv4z9c24ywm6'); set lines 155 col execs for 999,999,999 col avg_etime for 999,999.999 col avg_lio for 999,999,999.9 col begin_interval_time for a30 col node for 99999 break on plan_hash_value on startup_time skip 1 select ss.snap_id, ss.instance_number node, begin_interval_time, sql_id, plan_hash_value, nvl(executions_delta,0) execs, (elapsed_time_delta/decode(nvl(executions_delta,0),0,1,exe