11g新特性-如何禁用自動統計信息收集作業

一.11g中auto stats gather job被集成到了auto task中。

SQL> select client_name,status from DBA_AUTOTASK_CLIENT;

CLIENT_NAME                                                      STATUS
---------------------------------------------------------------- --------
auto optimizer stats collection                                  ENABLED
auto space advisor                                               ENABLED
sql tuning advisor                         ENABLED

SQl>select client_name,operation_name
  from dba_autotask_operation t;
------------------    ---------------------------
CLIENT_NAME           OPERATION_NAME
auto optimizer stats  collection auto optimizer stats job
auto space advisor   auto space advisor job
sql tuning advisor   automatic sql tuning task

可以通過以上視圖進行名字和狀態的查看。

禁用的時候，使用存儲過程逐個禁用。

SQL> begin
  2  DBMS_AUTO_TASK_ADMIN.DISABLE(client_name => 'sql tuning advisor',
  3  operation => NULL,
  4  window_name => NULL);
  5  end;
  6  /

PL/SQL procedure successfully completed.

SQL> select client_name,status from DBA_AUTOTASK_CLIENT;

CLIENT_NAME                                                      STATUS
---------------------------------------------------------------- --------
auto optimizer stats collection                                  DISABLED
auto space advisor                                               ENABLED
sql tuning advisor                                               DISABLED

 

二.在10G版本中,自動收集的job名字為:GATHER_STATS_JOB,默認情況下該job每天晚上10點執行.

1.查看該job的狀態以及執行情況

Select a.Enabled, Last_Start_Date, Next_Run_Date
  From Dba_Scheduler_Jobs a
 Where Job_Name = 'GATHER_STATS_JOB';

2.關閉和啟動該job

方法一：
exec dbms_scheduler.disable('SYS.GATHER_STATS_JOB');
exec dbms_scheduler.enable('SYS.GATHER_STATS_JOB');

方法二：
alter system set "_optimizer_autostats_job"=false scope=spfile;
alter system set "_optimizer_autostats_job"=true scope=spfile;

 

三.其他建議

對於數據量很大的庫，一般是建議關閉掉自動收集的任務，通過自己手工寫存儲過程，再把存儲過程加入JOB中去收集統計信息，統計信息的收集是根據表的大小來自己定義收集的采樣率以及其他的選項。

可以參考如下的存儲過程：

DECLARE
  CURSOR STALE_TABLE IS
    SELECT OWNER,
           SEGMENT_NAME,
           CASE
             WHEN SIZE_GB < 0.5 THEN
              30
             WHEN SIZE_GB >= 0.5 AND SIZE_GB < 1 THEN
              20
             WHEN SIZE_GB >= 1 AND SIZE_GB < 5 THEN
              10
             WHEN SIZE_GB >= 5 AND SIZE_GB < 10 THEN
              5
             WHEN SIZE_GB >= 10 THEN
              1
           END AS PERCENT,
           8 AS DEGREE
      FROM (SELECT OWNER,
                   SEGMENT_NAME,
                   SUM(BYTES / 1024 / 1024 / 1024) SIZE_GB
              FROM DBA_SEGMENTS
             WHERE OWNER = 'SCOTT'
               AND SEGMENT_NAME IN
                   (SELECT /*+ UNNEST */ DISTINCT TABLE_NAME
                      FROM DBA_TAB_STATISTICS
                     WHERE (LAST_ANALYZED IS NULL OR STALE_STATS = 'YES')
                       AND OWNER = 'SCOTT')
             GROUP BY OWNER, SEGMENT_NAME);
BEGIN
  DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO;
  FOR STALE IN STALE_TABLE LOOP
    DBMS_STATS.GATHER_TABLE_STATS(OWNNAME          => STALE.OWNER,
                                  TABNAME          => STALE.SEGMENT_NAME,
                                  ESTIMATE_PERCENT => STALE.PERCENT,
                                  METHOD_OPT       => 'for all columns size skewonly',
                                  DEGREE           => 8,
                                  GRANULARITY      => 'ALL',
                                  CASCADE          => TRUE);
  END LOOP;
END;

上述的存儲過程，先定義了表的大小所對應的采樣率，然后通過查詢DBA_SEGMENTS得到表的大小，再通過DBMS_STATS.GATHER_TABLE_STATS去收集統計信息。