每个行业都有自己的特点，比如金融行业，每天晚上10点左右会跑批，而自动收集统计信息默认周一到周五晚上10点，持续4个小时收集统计信息，周六周日每天6点，持续20个小时收集统计信息。显然我们应该设计一个更加合适的时间点来收集统计信息。

这里演示每天凌晨1点，持续5个小时收集统计信息的方法。

1.查看版本
SQL> select * from v$version;

BANNER                                                                               CON_ID
-------------------------------------------------------------------------------- ----------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production              0
PL/SQL Release 12.1.0.2.0 - Production                                                    0
CORE    12.1.0.2.0      Production                                                        0
TNS for Linux: Version 12.1.0.2.0 - Production                                            0
NLSRTL Version 12.1.0.2.0 - Production                                                    0

SQL> 

--默认值如下
set lines 200
col WINDOW_NAME for a20
col REPEAT_INTERVAL for a60 
col DURATION  for a20
SELECT w.window_name,
               w.repeat_interval,
               w.duration,
               w.enabled
          FROM dba_autotask_window_clients c, dba_scheduler_windows w
         WHERE c.window_name = w.window_name AND c.optimizer_stats = 'ENABLED';

SQL> set lines 200
SQL> col WINDOW_NAME for a20
SQL> col REPEAT_INTERVAL for a60 
SQL> col DURATION  for a20
SQL> SELECT w.window_name,
  2                 w.repeat_interval,
  3                 w.duration,
  4                 w.enabled
  5            FROM dba_autotask_window_clients c, dba_scheduler_windows w
  6           WHERE c.window_name = w.window_name AND c.optimizer_stats = 'ENABLED';

WINDOW_NAME          REPEAT_INTERVAL                                              DURATION             ENABL
-------------------- ------------------------------------------------------------ -------------------- -----
TUESDAY_WINDOW       freq=daily;byday=TUE;byhour=22;byminute=0; bysecond=0        +000 04:00:00        TRUE
WEDNESDAY_WINDOW     freq=daily;byday=WED;byhour=22;byminute=0; bysecond=0        +000 04:00:00        TRUE
THURSDAY_WINDOW      freq=daily;byday=THU;byhour=22;byminute=0; bysecond=0        +000 04:00:00        TRUE
FRIDAY_WINDOW        FREQ=daily;BYDAY=FRI;BYHOUR=22;BYMINUTE=30;BYSECOND=0        +000 04:00:00        TRUE
SATURDAY_WINDOW      freq=daily;byday=SAT;byhour=6;byminute=0; bysecond=0         +000 20:00:00        TRUE
SUNDAY_WINDOW        freq=daily;byday=SUN;byhour=6;byminute=0; bysecond=0         +000 20:00:00        TRUE

6 rows selected.

--修改自动收集统计信息每天凌晨一点，持续5个小时。
    --MONDAY
    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE (
            name        => '"SYS"."MONDAY_WINDOW"',
            attribute   => 'REPEAT_INTERVAL',
            VALUE       => 'FREQ=daily;BYDAY=MON;BYHOUR=1;BYMINUTE=0;BYSECOND=0');
        END;
    /

    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE(
        name => '"SYS"."MONDAY_WINDOW"',
        attribute => 'DURATION',
        value => numtodsinterval(300,'minute'));
     END;  
     /
    --TUESDAY
    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE (
            name        => '"SYS"."TUESDAY_WINDOW"',
            attribute   => 'REPEAT_INTERVAL',
            VALUE       => 'FREQ=daily;BYDAY=TUE;BYHOUR=1;BYMINUTE=0;BYSECOND=0');
        END;
    /

    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE(
        name => '"SYS"."TUESDAY_WINDOW"',
        attribute => 'DURATION',
        value => numtodsinterval(300,'minute'));
     END;  
     /

     --WEDNESDAY
     BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE (
            name        => '"SYS"."WEDNESDAY_WINDOW"',
            attribute   => 'REPEAT_INTERVAL',
            VALUE       => 'FREQ=daily;BYDAY=WED;BYHOUR=1;BYMINUTE=0;BYSECOND=0');
        END;
    /

    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE(
        name => '"SYS"."WEDNESDAY_WINDOW"',
        attribute => 'DURATION',
        value => numtodsinterval(300,'minute'));
     END;  
     /

     --THURSDAY
      BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE (
            name        => '"SYS"."THURSDAY_WINDOW"',
            attribute   => 'REPEAT_INTERVAL',
            VALUE       => 'FREQ=daily;BYDAY=THU;BYHOUR=1;BYMINUTE=0;BYSECOND=0');
        END;
    /

    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE(
        name => '"SYS"."THURSDAY_WINDOW"',
        attribute => 'DURATION',
        value => numtodsinterval(300,'minute'));
     END;  
     /

    --FRIDAY
     BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE (
            name        => '"SYS"."FRIDAY_WINDOW"',
            attribute   => 'REPEAT_INTERVAL',
            VALUE       => 'FREQ=daily;BYDAY=FRI;BYHOUR=1;BYMINUTE=0;BYSECOND=0');
        END;
    /

    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE(
        name => '"SYS"."FRIDAY_WINDOW"',
        attribute => 'DURATION',
        value => numtodsinterval(300,'minute'));
     END;  
     /
    --SATURDAY
    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE (
            name        => '"SYS"."SATURDAY_WINDOW"',
            attribute   => 'REPEAT_INTERVAL',
            VALUE       => 'FREQ=daily;BYDAY=SAT;BYHOUR=1;BYMINUTE=0;BYSECOND=0');
        END;
    /

    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE(
        name => '"SYS"."SATURDAY_WINDOW"',
        attribute => 'DURATION',
        value => numtodsinterval(300,'minute'));
     END;  
     /

    --SUNDAY
    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE (
            name        => '"SYS"."SUNDAY_WINDOW"',
            attribute   => 'REPEAT_INTERVAL',
            VALUE       => 'FREQ=daily;BYDAY=SUN;BYHOUR=1;BYMINUTE=0;BYSECOND=0');
        END;
    /

    BEGIN
        DBMS_SCHEDULER.SET_ATTRIBUTE(
        name => '"SYS"."SUNDAY_WINDOW"',
        attribute => 'DURATION',
        value => numtodsinterval(300,'minute'));
     END;  
     /

SQL> --验证是否变更
SQL> set lines 200
SQL> col WINDOW_NAME for a20
SQL> col REPEAT_INTERVAL for a60 
SQL> col DURATION  for a20
SQL> SELECT w.window_name,
  2                 w.repeat_interval,
  3                 w.duration,
  4                 w.enabled
  5            FROM dba_autotask_window_clients c, dba_scheduler_windows w
  6           WHERE c.window_name = w.window_name AND c.optimizer_stats = 'ENABLED';

WINDOW_NAME          REPEAT_INTERVAL                                              DURATION             ENABL
-------------------- ------------------------------------------------------------ -------------------- -----
MONDAY_WINDOW        FREQ=daily;BYDAY=MON;BYHOUR=1;BYMINUTE=0;BYSECOND=0          +000 05:00:00        TRUE
TUESDAY_WINDOW       FREQ=daily;BYDAY=TUE;BYHOUR=1;BYMINUTE=0;BYSECOND=0          +000 05:00:00        TRUE
WEDNESDAY_WINDOW     FREQ=daily;BYDAY=WED;BYHOUR=1;BYMINUTE=0;BYSECOND=0          +000 05:00:00        TRUE
THURSDAY_WINDOW      FREQ=daily;BYDAY=THU;BYHOUR=1;BYMINUTE=0;BYSECOND=0          +000 05:00:00        TRUE
FRIDAY_WINDOW        FREQ=daily;BYDAY=FRI;BYHOUR=1;BYMINUTE=0;BYSECOND=0          +000 05:00:00        TRUE
SATURDAY_WINDOW      FREQ=daily;BYDAY=SAT;BYHOUR=1;BYMINUTE=0;BYSECOND=0          +000 05:00:00        TRUE
SUNDAY_WINDOW        FREQ=daily;BYDAY=SUN;BYHOUR=1;BYMINUTE=0;BYSECOND=0          +000 05:00:00        TRUE

7 rows selected.

SQL> 

看到太多的客户都是默认值，当然对非7*24小时的系统也没有太大影响。但是，某些7X24小时的业务系统，我们需要做更多的优化调整，然后持续跟踪，不断优化。保证业务的连续性。不管大家有没有设置，都需要大家知道这里可能会引起性能问题的一个点，我们必须考虑到。