auto task for 11g



Oracle 11g 数据库有三个预定义自动维护任务：

Automatic Optimizer Statistics Collection（自动优化器统计信息收集）

收集数据库中所有无统计信息或仅有过时统计信息的 Schema 对象的 Optimizer（优化器）统计信息。SQL query optimizer（SQL 查询优化器）使用此任务收集的统计信息提高 SQL 执行的性能。

Automatic Segment Advisor（自动段指导）

识别有可用回收空间的段，并提出如何消除这些段中的碎片的建议。您也可以手动运行 Segment Advisor 获取更多最新建议，或获取 Automatic Segment Advisor 没有检查到的那些有可能做空间回收的段的建议。

Automatic SQL Tuning Advisor（自动 SQL 优化指导）

检查高负载 SQL 语句的性能，并提出如何优化这些语句的建议。您可以配置此指导，自动应用建议的SQL profile。

Note 466920.1  - 11g New Feature: Health Monitor

Note 755838.1 - New 11g Default Jobs

实施

它们在 Oracle10g 中为独立作业，且在 DBA_SCHEDULER_JOBS.JOB_NAME 中可见。

这在 Oracle11g 中有所更改。相关视图为 DBA_AUTOTASK_WINDOW_CLIENTS。
现在，这些作业只有当被真正执行时，才在 DBA_SCHEDULER_JOBS 中可见，且名称为系统生成的名称。

SQL> desc DBA_AUTOTASK_WINDOW_CLIENTS
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 WINDOW_NAME                               NOT NULL VARCHAR2(30)
 WINDOW_NEXT_TIME                                   TIMESTAMP(6) WITH TIME ZONE
 WINDOW_ACTIVE                                      VARCHAR2(5)
 AUTOTASK_STATUS                                    VARCHAR2(8)
 OPTIMIZER_STATS                                    VARCHAR2(8)
 SEGMENT_ADVISOR                                    VARCHAR2(8)
 SQL_TUNE_ADVISOR                                   VARCHAR2(8)
 HEALTH_MONITOR                                     VARCHAR2(8)

 select * from DBA_AUTOTASK_WINDOW_CLIENTS;

WINDOW_NAME
------------------------------
WINDOW_NEXT_TIME
---------------------------------------------------------------------------
WINDO AUTOTASK OPTIMIZE SEGMENT_ SQL_TUNE HEALTH_M
----- -------- -------- -------- -------- --------
MONDAY_WINDOW
08-DEC-08 10.00.00.000000 PM EUROPE/VIENNA
FALSE ENABLED ENABLED ENABLED ENABLED DISABLED

...

SUNDAY_WINDOW
07-DEC-08 06.00.00.000000 AM EUROPE/VIENNA
FALSE ENABLED ENABLED ENABLED ENABLED DISABLED
7 rows selected.

要启用或禁用所有窗口的所有自动维护任务，在不使用任何参数的情况下调用 ENABLE 或 DISABLE 程序。

SQL> execute DBMS_AUTO_TASK_ADMIN.DISABLE;

要禁用特定维护任务，使用 DISABLE 程序，如下所示：

SQL> BEGIN
       dbms_auto_task_admin.disable(
       client_name => 'sql tuning advisor',
       operation => NULL,
       window_name => NULL);
     END;  
    /

要再次启用该特定维护任务，使用 ENABLE 程序，如下所示：

SQL> BEGIN
       dbms_auto_task_admin.enable(
       client_name => 'sql tuning advisor',
       operation => NULL,
       window_name => NULL);
     END;
     /

client_name 参数使用的任务名称列在 DBA_AUTOTASK_CLIENT 数据库字典视图中。

示例：

auto optimizer stats collection
auto space advisor
sql tuning advisor

另一个差异是预定义调度程序窗口：

•   Oracle10g : WEEKNIGHT_WINDOW and WEEKEND_WINDOW
•   Oracle11g : MONDAY_WINDOW .... SUNDAY_WINDOW. 

为了向下兼容，WEEKNIGHT_WINDOW 和 WEEKEND_WINDOW 仍然存在。

窗口打开持续的时间在 11g 中有所更改。星期一到星期五从晚上 10 点到凌晨 2 点，星期六到星期日从上午 6 点到凌晨 2 点。

您可以使用 DBMS_SCHEDULER.SET_ATTRIBUTE 程序调整预定义维护窗口时间，使其适用于您的数据库环境。

示例：以下脚本将 WEEKNIGHT_WINDOW 改为每个工作日从午夜至上午 8 点（窗口持续时间为 8 小时不变）：

EXECUTE DBMS_SCHEDULER.SET_ATTRIBUTE(
'WEEKNIGHT_WINDOW', 
'repeat_interval',
'freq=daily;byday=MON, TUE, WED, THU, FRI;byhour=0;byminute=0;bysecond=0');

每个窗口还有一个名为 DEFAULT_MAINTENANCE_PLAN 的预定义资源计划，一旦打开相关窗口，该计划将激活。这是 10g 和 11g 之间的另一个差异。

SQL> select window_name, resource_plan from dba_scheduler_windows;

WINDOW_NAME                    RESOURCE_PLAN
------------------------------ ------------------------------
MONDAY_WINDOW                  DEFAULT_MAINTENANCE_PLAN
TUESDAY_WINDOW                 DEFAULT_MAINTENANCE_PLAN
WEDNESDAY_WINDOW               DEFAULT_MAINTENANCE_PLAN
THURSDAY_WINDOW                DEFAULT_MAINTENANCE_PLAN
FRIDAY_WINDOW                  DEFAULT_MAINTENANCE_PLAN
SATURDAY_WINDOW                DEFAULT_MAINTENANCE_PLAN
SUNDAY_WINDOW                  DEFAULT_MAINTENANCE_PLAN
WEEKNIGHT_WINDOW
WEEKEND_WINDOW

9 rows selected.

SQL> select * from dba_rsrc_plans where plan='DEFAULT_MAINTENANCE_PLAN'
PLAN_ID PLAN NUM_PLAN_DIRECTIVES
---------- ------------------------------ -------------------
CPU_METHOD MGMT_METHOD
------------------------------ ------------------------------
ACTIVE_SESS_POOL_MTH PARALLEL_DEGREE_LIMIT_MTH
------------------------------ ------------------------------
QUEUEING_MTH SUB
------------------------------ ---
COMMENTS
--------------------------------------------------------------------------------
STATUS MAN
------------------------------ ---
11187 DEFAULT_MAINTENANCE_PLAN 4
EMPHASIS EMPHASIS
ACTIVE_SESS_POOL_ABSOLUTE PARALLEL_DEGREE_LIMIT_ABSOLUTE
FIFO_TIMEOUT NO
Default plan for maintenance windows that prioritizes SYS_GROUP operations and a
llocates the remaining 5% to diagnostic operations and 25% to automated maintena
nce operations.
YES

SQL> select * from DBA_RSRC_PLAN_DIRECTIVES where plan='DEFAULT_MAINTENANCE_PLAN';

PLAN GROUP_OR_SUBPLAN TYPE
------------------------------ ------------------------------ --------------
CPU_P1 CPU_P2 CPU_P3 CPU_P4 CPU_P5 CPU_P6 CPU_P7
---------- ---------- ---------- ---------- ---------- ---------- ----------
CPU_P8 MGMT_P1 MGMT_P2 MGMT_P3 MGMT_P4 MGMT_P5 MGMT_P6
---------- ---------- ---------- ---------- ---------- ---------- ----------
MGMT_P7 MGMT_P8 ACTIVE_SESS_POOL_P1 QUEUEING_P1 PARALLEL_DEGREE_LIMIT_P1
---------- ---------- ------------------- ----------- ------------------------
SWITCH_GROUP SWITC SWITCH_TIME SWITCH_IO_MEGABYTES
------------------------------ ----- ----------- -------------------
SWITCH_IO_REQS SWITC MAX_EST_EXEC_TIME UNDO_POOL MAX_IDLE_TIME
-------------- ----- ----------------- ---------- -------------
MAX_IDLE_BLOCKER_TIME SWITCH_TIME_IN_CALL
--------------------- -------------------
COMMENTS
--------------------------------------------------------------------------------
STATUS MAN
------------------------------ ---
DEFAULT_MAINTENANCE_PLAN SYS_GROUP CONSUMER_GROUP
100 0 0 0 0 0 0
0 100 0 0 0 0 0
0 0
FALSE
FALSE

Directive for system operations
NO

DEFAULT_MAINTENANCE_PLAN OTHER_GROUPS CONSUMER_GROUP
0 70 0 0 0 0 0
0 0 70 0 0 0 0
0 0
FALSE
FALSE

Directive for all other operations
NO

DEFAULT_MAINTENANCE_PLAN ORA$AUTOTASK_SUB_PLAN PLAN
0 25 0 0 0 0 0
0 0 25 0 0 0 0
0 0
FALSE
FALSE

Directive for automated maintenance tasks
NO

DEFAULT_MAINTENANCE_PLAN ORA$DIAGNOSTICS CONSUMER_GROUP
0 5 0 0 0 0 0
0 0 5 0 0 0 0
0 0
FALSE
FALSE

Directive for automated diagnostic tasks
NO

10g 与 11g 之间变化的摘要：

主题	10g	11g
作业	在 DBA_SCHEDULER_JOBS 中独立作业	AUTOTASKS 有命名前缀“ORA$AT”，且只有作业执行后才可见
维护窗口	2 个窗口：WEEKNIGHT 和 WEEKEND	每天有不同的窗口
Resource manager	默认不启用	每个窗口都有预定义资源计划

相关视图：

DBA_AUTOTASK_CLIENT
DBA_AUTOTASK_CLIENT_HISTORY
DBA_AUTOTASK_CLIENT_JOB
DBA_AUTOTASK_JOB_HISTORY
DBA_AUTOTASK_OPERATION
DBA_AUTOTASK_SCHEDULE
DBA_AUTOTASK_TASK
DBA_AUTOTASK_WINDOW_CLIENTS
DBA_AUTOTASK_WINDOW_HISTORY

References

NOTE:466920.1 - 11g New Feature: Health monitor
NOTE:755838.1 - New 11g Default Jobs

NOTE:858852.1 - DBA_AUTOTASK_TASK and DBA_AUTOTASK_CLIENT Shows Different Status For Auto Optimizer Stats Collection

SELECT * FROM dba_tab_stats_history 查看表统计时间

SELECT window_name, job_name, job_duration
FROM DBA_AUTOTASK_JOB_HISTORY 
WHERE JOB_NAME like 'ORA$AT_OS%';

Login as SYSDBA



@?/rdbms/admin/catnomwn.sql -- this drops the maintenance window, it will give some errors that can be ignored.



-- Drop the windows manually:

execute dbms_scheduler.drop_window('MONDAY_WINDOW');

execute dbms_scheduler.drop_window('TUESDAY_WINDOW');

execute dbms_scheduler.drop_window('WEDNESDAY_WINDOW');

execute dbms_scheduler.drop_window('THURSDAY_WINDOW');

execute dbms_scheduler.drop_window('FRIDAY_WINDOW');

execute dbms_scheduler.drop_window('SATURDAY_WINDOW');

execute dbms_scheduler.drop_window('SUNDAY_WINDOW');



@?/rdbms/admin/catmwin.sql -- this recreates it

set pages 1000
column WINDOW_NAME format a16
column WINDOW_NEXT_TIME format a38
column WINDOW_ACTIVE format a5
column OPTIMIZER_STATS format a10

select WINDOW_NAME, WINDOW_NEXT_TIME , WINDOW_ACTIVE,OPTIMIZER_STATS from DBA_AUTOTASK_WINDOW_CLIENTS order by WINDOW_NEXT_TIME ;

column next_start_date format a36
column comments format a38
select window_group_name, enabled, number_of_windows, next_start_date, comments from dba_scheduler_window_groups;

SQL> select client_name, status, window_group from DBA_AUTOTASK_CLIENT;

1.  Statistics_level must NOT BE = basic.  Should be =TYPICAL otherwise stats not collected.

sqlplus / as sysdba
show parameter statistics_level

NAME                                               TYPE        VALUE                                                                                                
-------------------------------------------------- ----------- ---------------------------------------------------------------------------------------------------- 
statistics_level                                   string      TYPICAL                                                                                              

 

2.  Are the autotasks (3 of them) listed and ENABLED?

set pages 1000
select client_name, status, window_group from dba_autotask_client;

3.  Check the Windows and WINDOW_NEXT_TIME for day returned.

select * from DBA_AUTOTASK_WINDOW_CLIENTS;

4.  This checks history of the optimizer collection.

col job_name format a23
col job_start_time format a40
col job_duration format a14
select job_name, job_start_time, job_duration
from DBA_AUTOTASK_JOB_HISTORY
where client_name like 'auto optimizer stats collection'
order by job_start_time; 

5) Here is command to enable autotask.

 -->  execute DBMS_AUTO_TASK_ADMIN.ENABLE;

Then AUTOTASK_STATUS in DBA_AUTOTASK_WINDOW_CLIENTS view will show ENABLED for all Windows.

 

6) To manually run, just to ensure at least 1 run:

SQL> exec DBMS_AUTO_TASK_IMMEDIATE.GATHER_OPTIMIZER_STATS;

7) Recheck history using the query in #4.

6) If ever there is a large data load (ie - HR2HR or other import), manually run the job (step 4) when you are satisfied that the data load is finished and successful.

In 11g, the automated maintenance task that collects statistics is called 'auto optimizer stats collection'. You can determine its status by selecting fromDBA_AUTOTASK_CLIENT:

SELECT CLIENT_NAME,
       STATUS
FROM   DBA_AUTOTASK_CLIENT
WHERE  CLIENT_NAME = 'auto optimizer stats collection'
/

CLIENT_NAME                                                      STATUS
---------------------------------------------------------------- --------
auto optimizer stats collection                                  ENABLED

The DBA_AUTOTASK_CLIENT view also displays frequency information about current and past automated maintenance tasks in columns MEAN_INCOMING_TASKS_7_DAYS and MEAN_INCOMING_TASKS_30_DAYS so you can see this historical information using a query like:

SELECT CLIENT_NAME               ,
       STATUS                    ,
       MEAN_INCOMING_TASKS_7_DAYS,
       MEAN_INCOMING_TASKS_30_DAYS
FROM   DBA_AUTOTASK_CLIENT
WHERE  CLIENT_NAME = 'auto optimizer stats collection'
/

•  How to enable auto stats collection?

If for some reason automatic optimizer statistics collection is disabled, you can enable it using the ENABLE procedure in the DBMS_AUTO_TASK_ADMIN package:

exec DBMS_AUTO_TASK_ADMIN.ENABLE(
client_name => 'auto optimizer stats collection',  
operation => NULL,  
window_name => NULL);

 

•  How to disable the auto stats collection?

In situations when you want to disable automatic optimizer statistics collection, you can disable it using the DISABLE procedure in the DBMS_AUTO_TASK_ADMIN package:

exec DBMS_AUTO_TASK_ADMIN.DISABLE(
client_name => 'auto optimizer stats collection',  
operation => NULL,  
window_name => NULL);

 

For details of the other columns in DBA_AUTOTASK_CLIENT,see:

Oracle Database Reference
11g Release 2 (11.2)
Part Number E25513-01
http://docs.oracle.com/cd/E11882_01/server.112/e25513/statviews_3084.htm

NOTE that the status in DBA_AUTOTASK_TASK and DBA_AUTOTASK_CLIENT may be different. See:

Document 858852.1  DBA_AUTOTASK_TASK and DBA_AUTOTASK_CLIENT Shows Different Status For Auto Optimizer Stats Collection

10g

The following is the 'old method' for checking the current and past automated maintenance tasks:

SELECT j.job_name     ,
       j.program_name ,
       j.schedule_name,
       j.job_class    ,
       p.enabled
FROM   dba_scheduler_programs p,
       dba_scheduler_jobs j
WHERE  p.program_name=j.program_name;


JOB_NAME
------------------------------
PROGRAM_NAME
--------------------------------------------------------------------------------
SCHEDULE_NAME
--------------------------------------------------------------------------------
JOB_CLASS                      ENABL
------------------------------ -----
..
GATHER_STATS_JOB
GATHER_STATS_PROG
MAINTENANCE_WINDOW_GROUP
AUTO_TASKS_JOB_CLASS           TRUE

 

• How do you disable the GATHER_STATS_JOB for 10g?

  The most direct approach is to disable the GATHER_STATS_JOB as follows:
  
  
  SQL> exec sys.dbms_scheduler.disable ('GATHER_STATS_JOB');

• How do you enable the GATHER_STATS_JOB for 10g?

  This is enabled by default. If you have disabled it, then you can re-enable it as
  
  
  SQL> exec sys.dbms_scheduler.enable (€"SYS"."GATHER_STATS_JOB");

Note: If the 10g method is used on 11g, then it does not return any information as the implementation is quite different in 11g:

Connected to:
Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - Production
With the Partitioning and Real Application Testing options

SQL> SELECT job_name     ,
       job_type     ,
       program_name ,
       schedule_name,
       job_class
FROM   dba_scheduler_jobs
WHERE  job_name = 'GATHER_STATS_JOB';

no rows selected

11g中统计信息自动收集任务的名称是auto optimizer stats collection。11g中自动任务默认的执行时间窗口为：
    周一到周五是晚上10点开始到2点结束
    周末是早上六点，持续20个小时。
1、查看自动收集任务及状态

select client_name,status from Dba_Autotask_Client where client_name='auto optimizer stats collection';

2、停止自动收集任务

SQL> BEGIN
  2      DBMS_AUTO_TASK_ADMIN.DISABLE(
  3                     client_name => 'auto optimizer stats collection',
  4                     operation => NULL, window_name => NULL);
  5  END;
  6  /

PL/SQL procedure successfully completed.

SQL> select client_name,status from Dba_Autotask_Client where client_name='auto optimizer stats collection';

CLIENT_NAME                                                      STATUS
---------------------------------------------------------------- --------
auto optimizer stats collection                                  DISABLED

但是此时再查询DBA_ATUOTASK_TASK视图时，显示该任务状态还是ENABLED

SQL> select client_name,status from dba_autotask_task where client_name='auto optimizer stats collection';

CLIENT_NAME                                                      STATUS
---------------------------------------------------------------- --------
auto optimizer stats collection                                  ENABLED

Oracle给出的解释是在现在的版本中（11.1 to 11.2）一个client对应一个task，但是在将来的版本中会出现多个client会对应一个task，所以一个client被disabled了，不会改变task的状态。[ID 858852.1]
3、启动自动收集任务

SQL> BEGIN
  2      DBMS_AUTO_TASK_ADMIN.ENABLE(
  3                     client_name => 'auto optimizer stats collection',
  4                     operation => NULL, window_name => NULL);
  5  END;
  6  /

PL/SQL procedure successfully completed.

SQL> select client_name,status from Dba_Autotask_Client where client_name='auto optimizer stats collection';

CLIENT_NAME                                                      STATUS
---------------------------------------------------------------- --------
auto optimizer stats collection                                  ENABLED 

4、查看自动收集任务历史执行状态

 SQL> SELECT client_name, window_name, jobs_created, jobs_started, jobs_completed
  2   FROM dba_autotask_client_history
  3   WHERE client_name like '%stats%';

CLIENT_NAME                              WINDOW_NAME                    JOBS_CREATED JOBS_STARTED JOBS_COMPLETED
---------------------------------------- ------------------------------ ------------ ------------ --------------
auto optimizer stats collection          SATURDAY_WINDOW                           5            5              5
auto optimizer stats collection          SUNDAY_WINDOW                             6            6              6

通过时间窗口名称可以看出是周几执行的，在时间窗口内创建了几次job，执行了几次job，当然可以加上window_start_time来查看具体执行的日期。
5、查看自动收集任务执行时间窗口

		

			SQL> select WINDOW_NAME, WINDOW_NEXT_TIME , WINDOW_ACTIVE,OPTIMIZER_STATS from DBA_AUTOTASK_WINDOW_CLIENTS order by WINDOW_NEXT_TIME ;
		

		

			WINDOW_NAME                    WINDOW_NEXT_TIME                                WINDO OPTIMIZE
------------------------------ ----------------------------------------------- ----- --------
MONDAY_WINDOW                  26-NOV-12 10.00.00.000000 PM PRC                TRUE  ENABLED
TUESDAY_WINDOW                 27-NOV-12 10.00.00.000000 PM PRC                FALSE ENABLED
WEDNESDAY_WINDOW               28-NOV-12 10.00.00.000000 PM PRC                FALSE ENABLED
THURSDAY_WINDOW                29-NOV-12 10.00.00.000000 PM PRC                FALSE ENABLED
FRIDAY_WINDOW                  30-NOV-12 10.00.00.000000 PM PRC                FALSE ENABLED
SATURDAY_WINDOW                01-DEC-12 06.00.00.000000 AM PRC                FALSE ENABLED
SUNDAY_WINDOW                  02-DEC-12 06.00.00.000000 AM PRC                FALSE ENABLED
		

我将系统日期改为11月26日22点以后，MONDAY_WINDOW执行时间窗口自动激活。
6、查询自动收集任务正在执行的JOB

select client_name, JOB_SCHEDULER_STATUS from DBA_AUTOTASK_CLIENT_JOB where client_name='auto optimizer stats collection';

这个查询没有结果也很正常，只有job正在运行时，该查询才有结果。
7、与时间窗口相关的视图
查询自动收集任务所属时间窗口组

SQL> select client_name,window_group from dba_autotask_client where client_name='auto optimizer stats collection';

CLIENT_NAME                              WINDOW_GROUP
---------------------------------------- ---------------------------------------------------
auto optimizer stats collection          ORA$AT_WGRP_OS

查询自动收集任务所属时间窗口组详细信息

SQL> select * from dba_scheduler_window_groups where window_group_name='ORA$AT_WGRP_OS';

WINDOW_GROUP_NA ENABL NUMBER_OF_WINDOWS NEXT_START_DATE                     COMMENTS
--------------- ----- ----------------- ----------------------------------- ---------------------------------------------
ORA$AT_WGRP_OS  TRUE                  7 26-NOV-12 10.00.00.000000 PM PRC    auto optimizer stats collection

查看自动收集任务所属时间窗口组包含的子时间窗口

SQL> select * from dba_scheduler_wingroup_members where window_group_name='ORA$AT_WGRP_OS';

WINDOW_GROUP_NA WINDOW_NAME
--------------- ------------------------------
ORA$AT_WGRP_OS  MONDAY_WINDOW
ORA$AT_WGRP_OS  TUESDAY_WINDOW
ORA$AT_WGRP_OS  WEDNESDAY_WINDOW
ORA$AT_WGRP_OS  THURSDAY_WINDOW
ORA$AT_WGRP_OS  FRIDAY_WINDOW
ORA$AT_WGRP_OS  SATURDAY_WINDOW ORA$AT_WGRP_OS  SUNDAY_WINDOW

查看子时间窗口信息

SQL> select a.window_name,a.next_start_date,a.active from dba_scheduler_windows a
  2  inner join dba_scheduler_wingroup_members b on a.window_name = b.window_name
  3  where b.window_group_name='ORA$AT_WGRP_OS';

WINDOW_NAME                    NEXT_START_DATE                     ACTIV
------------------------------ ----------------------------------- -----
MONDAY_WINDOW                  26-NOV-12 10.00.00.000000 PM PRC    TRUE
TUESDAY_WINDOW                 27-NOV-12 10.00.00.000000 PM PRC    FALSE
WEDNESDAY_WINDOW               28-NOV-12 10.00.00.000000 PM PRC    FALSE
THURSDAY_WINDOW                29-NOV-12 10.00.00.000000 PM PRC    FALSE
FRIDAY_WINDOW                  30-NOV-12 10.00.00.000000 PM PRC    FALSE
SATURDAY_WINDOW                01-DEC-12 06.00.00.000000 AM PRC    FALSE
SUNDAY_WINDOW                  02-DEC-12 06.00.00.000000 AM PRC    FALSE

通过这个查询可以看出DBA_AUTOTASK_WINDOW_CLIENTS视图的信息其实和上面的结果一样。

总结一下统计信息自动收集任务运行的步骤：
首先是dba_autotask_task-->dba_autotask_client建立自动执行任务
再根据时间窗口及资源组建立自动执行作业
dba_autotask_client-->dba_scheduler_window_groups-->dba_scheduler_windows
                                                                                                                                    -->dba_scheduler_jobs
dba_autotask_client-->dba_scheduler_job_classes
相关视图：
dba_autotask_task
dba_autotask_client
dba_autotask_client_job
dba_autotask_window_clients
dba_autotask_client_history

dba_scheduler_jobs
dba_scheduler_job_classes
dba_scheduler_window_groups
dba_scheduler_windows
dba_scheduler_wingroup_members

自定义自动收集任务时间窗口：
How to use an own Maintenance Window for the Statistics Collection in 11g [ID 1300313.1]

MOS相关文档： FAQ: Automatic Statistics Collection [ID 1233203.1]