Oracle introduced statistics

Statistics automatically perform requires the following conditions are met:

dba_autotask_task 字段status值 ENABLED
dba_autotask_client status field value ENABLED
dba_autotask_window_clients 字段AUTOTASK_STATUS值 ENABLED OPTIMIZER_STATS值 ENABLED WINDOW_ACTIVE值 FALSE
dba_scheduler_windows field value ENABLED TRUE field ACTIVE value FALSE field DURATION value is greater than 10 minutes
dba_scheduler_jobs field value ENABLED TRUE

To summarize the steps statistics collection task to run automatically:

The first is dba_autotask_task -> dba_autotask_client set up an automated task

And then set up an automated job based on the time window and Resource Group

dba_autotask_client-->dba_scheduler_window_groups-->dba_scheduler_windows-->dba_scheduler_jobs

dba_autotask_client-->dba_scheduler_job_classes

1, statistics on the implementation of the general task view view dba_autotask_task

2, the total process view call statistics view dba_scheduler_programs

3, the execution state dba_autotask_client statistics, can be modified by performing DBMS_AUTO_TASK_ADMIN packet, updates the status field and dba_autotask_window_clients dba_autotask_client of OPTIMIZER_STATS, SEGMENT_ADVISOR, SQL_TUNE_ADVISOR field.

 1 BEGIN
 2   DBMS_AUTO_TASK_ADMIN.enable(client_name => 'auto optimizer stats collection',
 3                               operation   => NULL,
 4                               window_name => 'MONDAY_WINDOW');
 5 END;
 6  
 7 BEGIN
 8   DBMS_AUTO_TASK_ADMIN.disable(client_name => 'auto optimizer stats collection',
 9                                operation   => NULL,
10                                window_name => NULL);
11 END;

4. If you do DBMS_AUTO_TASK_ADMIN package without parameters, change dba_autotask_window_clients field of AUTOTASK_STATUS

1 BEGIN
2   DBMS_AUTO_TASK_ADMIN.enable();
3 END;
4 BEGIN
5   DBMS_AUTO_TASK_ADMIN.disable();
6 END;

5, various views dba_scheduler_windows perform detailed statistical information such as the attribute (the execution time, execution duration) can be provided by

 1 --设置开始时间
 2 BEGIN
 3   DBMS_SCHEDULER.SET_ATTRIBUTE(name      => '"SYS"."WEDNESDAY_WINDOW"',
 4                                attribute => 'REPEAT_INTERVAL',
 5                                value     => 'freq=daily;byday=WED;byhour=07;byminute=46;bysecond=0');
 6 END;
 7 --设置执行时长，如果设置值小于10分钟，统计信息貌似不能搜集
 8 BEGIN
 9   DBMS_SCHEDULER.SET_ATTRIBUTE(name      => '"SYS"."WEDNESDAY_WINDOW"',
10                                attribute => 'DURATION',
11                                VALUE     => '+000 00:20:00');
12 END;
13 --禁用窗口，禁用后dba_autotask_window_clients视图相关信息消失
14 BEGIN
15   dbms_scheduler.disable(name => 'WEDNESDAY_WINDOW', force => TRUE);
16 END;
17 --启用窗口
18 BEGIN
19   dbms_scheduler.enable(name => 'WEDNESDAY_WINDOW');
20 END;
21 --停止JOB
22 BEGIN
23   dbms_scheduler.stop_job('ORA$AUTOTASK_CLEAN');
24 END;
25 --手动打开窗口
26 BEGIN
27   dbms_scheduler.open_window('WEDNESDAY_WINDOW');
28 END;
29 --关闭窗口
30 BEGIN
31   dbms_scheduler.close_window('WEDNESDAY_WINDOW');
32 END;

注：在窗口执行的过程中dba_scheduler_windows视图ACTIVE字段是true状态，dba_autotask_window_clients视图WINDOW_ACTIVE字段也只true状态

表统计信息收集标识：

　　一个表中被修改的行数超过stale_percent(缺省值10%)时就会认为这个表的统计数据过时了。oracle会监控所有表的DML活动并在SGA中进行记录。监控的信息会定时的刷新到磁盘且可以通过*_tab_modifications视图来查看。

　　也可以调用dbms_stats.flush_database_monitoring_info过程来手动刷新这些数据.如果想在查询时得到最新信息(在所有统计数据收集之前内部监控数据会被刷新).可以通过查询user_tab_statistics视图中的stale_stats列来查看哪个表的统计数据过时了。表的stale_stats被设置为NO,统计数据是最新的.表的stale_stats被设置为YES,统计数据是过时的.表的stale_stats没有被设置说明丢失统计数据.

Oracle introduced statistics

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