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Oracle手动固定SQL执行计划

      在运维过程中,我们经常会遇到Oracle由于数据、统计信息等的变动,导致Oracle CBO选择不是我们期望的执行计划的情况,下面记录一下手动固定执行计划的过程。
1、查询每个执行计划消耗的资源情况
SQL> set lines 150 pages 999;
SQL> col p_user for 99999 ;
SQL> col execs  for 9999999 ;
SQL> select a.INSTANCE_NUMBER inst_id,to_char(b.END_INTERVAL_TIME,'yyyymmdd hh24:mi:ss') time,plan_hash_value,buffer_gets_delta/executions_delta get_exec, disk_reads_delta/executions_delta read_exec,cpu_time_delta/executions_delta/1000 cpu_exec_ms  ,elapsed_time_delta/executions_delta/1000 elaps_exec_ms  ,parsing_schema_id p_user,ROWS_PROCESSED_delta/executions_delta rows_exec,EXECUTIONS_DELTA execs
  2  from dba_hist_sqlstat a, dba_hist_snapshot b
  3  where a.sql_id='bq6kas7t6x9vh'
  4  and a.snap_id = b.snap_id
  5  and a.instance_number = b.instance_number
  6  and b.END_INTERVAL_TIME between sysdate - 3 and sysdate
  7  and executions_delta>0  order by 2,1;
------------------------Created by Tangyun[Tony.Tang]------------------------
   INST_ID TIME              PLAN_HASH_VALUE   GET_EXEC  READ_EXEC CPU_EXEC_MS ELAPS_EXEC_MS P_USER  ROWS_EXEC    EXECS
---------- ----------------- --------------- ---------- ---------- ----------- ------------- ------ ---------- --------
         1 20151125 11:00:15       402930455        133          0  6.33266667         6.744     46 19.3333333        3
         1 20151125 11:00:15      3783743255 144.666667 .333333333      8.1655          8.42     46 23.8333333        6
         1 20151125 11:00:15      1639688791        100          0       4.666    4.99166667     46 13.6666667        3
         1 20151125 12:00:18      3783743255 104.230769          0  7.30661538    12.2459231     46 18.9230769       13
         1 20151125 12:00:18       402930455         78          0  5.66633333    8.95633333     46         13        3
         1 20151125 12:00:18      1639688791      127.5          0      6.9985         7.252     46       11.5        2
         1 20151125 13:00:21      1639688791 218.375671  .00017316  .886103896    .872582251     46 24.1582684    11550
         1 20151125 14:00:23      1639688791 211.849579          0  .842681107     .83075722     46 22.2030686     6648
         1 20151125 15:00:26      1639688791 221.616694          0  .915307131    .903271745     46 26.3946515     3702


9 rows selected.
------------------------Created by Tangyun[Tony.Tang]------------------------

2、固定执行计划为 1639688791。
SQL> select sql_handle, plan_name, accepted, fixed,optimizer_cost from dba_sql_plan_baselines ;

no rows selected

SQL> var n number
SQL> begin
  2  :n:=dbms_spm.load_plans_from_cursor_cache(sql_id=>'bq6kas7t6x9vh', plan_hash_value=>1639688791, fixed =>'YES', enabled=>'YES');
  3  end;
  4  /

PL/SQL procedure successfully completed.


SQL> select sql_handle, plan_name, accepted, fixed,optimizer_cost from dba_sql_plan_baselines


SQL_HANDLE                     PLAN_NAME                      ACC FIX OPTIMIZER_COST
------------------------------ ------------------------------ --- --- --------------
QL_368f6240d3b95ad6           SQL_PLAN_3d3v2839vkqqqa3c44420 YES YES             34




----删除固定执行计划的方法BEGIN-------
declare 
xx PLS_INTEGER; 
BEGIN 
xx :=dbms_spm.drop_sql_plan_baseline(sql_handle=>'SQL_PLAN_3d3v2839vkqqqa3c44420',plan_name=>null); 
END; 
/
----删除固定执行计划的方法END-------
------------------------Created by Tangyun[Tony.Tang] 2016.03------------------------
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