Oracle数据库自己会例行做一些定时任务，比如会自动进行统计信息收集等作业任务。如果统计信息收集的时间正好赶上业务的高峰期，那就有可能由此引发一系列性能故障。
那么，我们该如何查看这些数据库自动去做的任务执行计划和执行情况呢？
1.计划窗口调整
首先，通过查询dba_scheduler_windows，可以看到有关窗口的定义详情。
SQL>
col window_name for a30
col REPEAT_INTERVAL for a60
set lines 180
select window_name,repeat_interval,duration,enabled from dba_scheduler_windows;
如果数据库是10g版本，结果如下：
SQL> select window_name,repeat_interval,duration,enabled from dba_scheduler_windows;
WINDOW_NAME REPEAT_INTERVAL DURATION ENABL
------------------------------ ------------------------------------------------------------ --------------------------------------------------------------------------- -----
WEEKNIGHT_WINDOW freq=daily;byday=MON,TUE,WED,THU,FRI;byhour=22;byminute=0; b +000 08:00:00 TRUE
ysecond=0
WEEKEND_WINDOW freq=daily;byday=SAT;byhour=0;byminute=0;bysecond=0 +002 00:00:00 TRUE
如果数据库是11g和12c版本，则是类似这样的结果：
SQL> select window_name,repeat_interval,duration,enabled from dba_scheduler_windows;
WINDOW_NAME REPEAT_INTERVAL DURATION ENABL
------------------------------ ------------------------------------------------------------ --------------------------------------------------------------------------- -----
WEEKEND_WINDOW freq=daily;byday=SAT;byhour=0;byminute=0;bysecond=0 +002 00:00:00 FALSE
WEEKNIGHT_WINDOW freq=daily;byday=MON,TUE,WED,THU,FRI;byhour=22;byminute=0; b +000 08:00:00 FALSE
ysecond=0
SUNDAY_WINDOW freq=daily;byday=SUN;byhour=6;byminute=0; bysecond=0 +000 20:00:00 TRUE
SATURDAY_WINDOW freq=daily;byday=SAT;byhour=6;byminute=0; bysecond=0 +000 20:00:00 TRUE
FRIDAY_WINDOW freq=daily;byday=FRI;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
WEDNESDAY_WINDOW freq=daily;byday=WED;byhour=22;byminute=0; bysecond=0 +000 04:00:00 TRUE
TUESDAY_WINDOW freq=daily;byday=TUE;byhour=22;byminute=0; bysecond=0 +000 04:00:00 TRUE
MONDAY_WINDOW freq=daily;byday=MON;byhour=22;byminute=0; bysecond=0 +000 04:00:00 TRUE
可以看到，在11g之后，oracle将之前只区分工作日和休息日的分类，细化到一周中的每一天。而且默认值的收集时间也比10g有大幅度的减少。
修改窗口启动时间和duration：
--修改窗口启动时间
EXEC DBMS_SCHEDULER.SET_ATTRIBUTE('MONDAY_WINDOW','repeat_interval','freq=daily;byday=MON;byhour=22;byminute=0;bysecond=0');
EXEC DBMS_SCHEDULER.SET_ATTRIBUTE('TUESDAY_WINDOW','repeat_interval','freq=daily;byday=TUE;byhour=22;byminute=0;bysecond=0');
EXEC DBMS_SCHEDULER.SET_ATTRIBUTE('WEDNESDAY_WINDOW','repeat_interval','freq=daily;byday=WED;byhour=22;byminute=0;bysecond=0');
EXEC DBMS_SCHEDULER.SET_ATTRIBUTE('THURSDAY_WINDOW','repeat_interval','freq=daily;byday=THU;byhour=22;byminute=0;bysecond=0');
EXEC DBMS_SCHEDULER.SET_ATTRIBUTE('FRIDAY_WINDOW','repeat_interval','freq=daily;byday=FRI;byhour=22;byminute=0;bysecond=0');
EXEC DBMS_SCHEDULER.SET_ATTRIBUTE('SATURDAY_WINDOW','repeat_interval','freq=daily;byday=SAT;byhour=6;byminute=0;bysecond=0');
EXEC DBMS_SCHEDULER.SET_ATTRIBUTE('SUNDAY_WINDOW','repeat_interval','freq=daily;byday=SUN;byhour=6;byminute=0;bysecond=0');
--修改窗口duration
exec dbms_scheduler.set_attribute('MONDAY_WINDOW','duration',numtodsinterval(240,'minute'));
exec dbms_scheduler.set_attribute('TUESDAY_WINDOW','duration',numtodsinterval(240,'minute'));
exec dbms_scheduler.set_attribute('WEDNESDAY_WINDOW','duration',numtodsinterval(240,'minute'));
exec dbms_scheduler.set_attribute('THURSDAY_WINDOW','duration',numtodsinterval(240,'minute'));
exec dbms_scheduler.set_attribute('FRIDAY_WINDOW','duration',numtodsinterval(240,'minute'));
exec dbms_scheduler.set_attribute('SATURDAY_WINDOW','duration',numtodsinterval(1200,'minute'));
exec dbms_scheduler.set_attribute('SUNDAY_WINDOW','duration',numtodsinterval(1200,'minute'));
以上实际都是Oracle默认的值（周一到周五每晚10点开始收集统计信息，duration是4h；周六周日早上6点开始收集统计信息，duration是20h），可以根据实际业务需求进行调整。
很多周六日业务量也很大的企业，一定要注意调整这个默认值。
2.自动任务调整
10g版本没有这些自动维护任务，以下都是以11g以上版本为例，主要介绍如何关闭／启用自动任务（默认是关闭的。）。
查询： select client_name,status from dba_autotask_client;
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
关闭自动维护任务：
--关闭sql tuning advisor,避免消耗过多的资源
BEGIN
DBMS_AUTO_TASK_ADMIN.disable(
client_name => 'sql tuning advisor',
operation => NULL,
window_name => NULL);
END;
/
--关闭auto space advisor,避免消耗过多的IO，还有避免出现这个任务引起的library cache lock
BEGIN
DBMS_AUTO_TASK_ADMIN.disable(
client_name => 'auto space advisor',
operation => NULL,
window_name => NULL);
END;
/
--光闭自动统计信息收集，（慎用，除非有其他手工收集统计信息的完整方案，否则不建议关闭）
BEGIN
DBMS_AUTO_TASK_ADMIN.disable(
client_name => 'auto optimizer stats collection',
operation => NULL,
window_name => NULL);
END;
/
启动自动维护任务：
--启动sql tuning advisor
BEGIN
DBMS_AUTO_TASK_ADMIN.enable(
client_name => 'sql tuning advisor',
operation => NULL,
window_name => NULL);
END;
/
--启动auto space advisor
BEGIN
DBMS_AUTO_TASK_ADMIN.enable(
client_name => 'auto space advisor',
operation => NULL,
window_name => NULL);
END;
/
--启动自动统计信息收集
BEGIN
DBMS_AUTO_TASK_ADMIN.enable(
client_name => 'auto optimizer stats collection',
operation => NULL,
window_name => NULL);
END;
/
3.任务执行情况
主要查询这个视图：dba_scheduler_job_run_details
SQL>
col job_name for a30
col ACTUAL_START_DATE for a40
col RUN_DURATION for a30
set lines 180 pages 100
--10g
select owner, job_name, status, ACTUAL_START_DATE, RUN_DURATION from dba_scheduler_job_run_details where job_name = 'GATHER_STATS_JOB' order by 4;
10g版本查询结果类似如下：
OWNER JOB_NAME STATUS ACTUAL_START_DATE RUN_DURATION
------------------------------ ------------------------------ ------------------------------ ---------------------------------------- ------------------------------
SYS GATHER_STATS_JOB SUCCEEDED 31-OCT-17 10.00.02.512503 AM +08:00 +000 00:00:41
SYS GATHER_STATS_JOB SUCCEEDED 01-NOV-17 10.00.03.102893 AM +08:00 +000 00:00:53
SYS GATHER_STATS_JOB SUCCEEDED 02-NOV-17 10.00.02.822735 AM +08:00 +000 00:02:19
SYS GATHER_STATS_JOB SUCCEEDED 03-NOV-17 10.00.03.635398 AM +08:00 +000 00:00:54
SYS GATHER_STATS_JOB SUCCEEDED 04-NOV-17 10.00.04.819712 AM +08:00 +000 00:01:25
SYS GATHER_STATS_JOB SUCCEEDED 04-NOV-17 06.00.03.443851 PM +08:00 +000 00:00:16
SYS GATHER_STATS_JOB STOPPED 09-NOV-17 11.00.03.008706 AM +08:00 +005 01:30:12
SYS GATHER_STATS_JOB SUCCEEDED 15-NOV-17 11.00.01.423370 AM +08:00 +000 00:01:39
SYS GATHER_STATS_JOB SUCCEEDED 16-NOV-17 11.00.03.842124 AM +08:00 +000 00:00:43
SYS GATHER_STATS_JOB SUCCEEDED 17-NOV-17 11.00.01.535534 AM +08:00 +000 00:00:43
SYS GATHER_STATS_JOB SUCCEEDED 21-NOV-17 11.00.02.590796 AM +08:00 +000 00:01:04
SYS GATHER_STATS_JOB SUCCEEDED 24-NOV-17 11.00.02.291902 AM +08:00 +000 00:00:44
SYS GATHER_STATS_JOB SUCCEEDED 25-NOV-17 11.00.02.660842 AM +08:00 +000 00:01:04
SYS GATHER_STATS_JOB SUCCEEDED 25-NOV-17 07.00.02.587985 PM +08:00 +000 00:00:40
SYS GATHER_STATS_JOB SUCCEEDED 28-NOV-17 11.00.01.916662 AM +08:00 +000 00:01:08
SYS GATHER_STATS_JOB SUCCEEDED 29-NOV-17 11.00.03.060642 AM +08:00 +000 00:00:38
SYS GATHER_STATS_JOB SUCCEEDED 30-NOV-17 11.00.00.737144 AM +08:00 +000 00:01:45
--11g
select owner, job_name, status, ACTUAL_START_DATE, RUN_DURATION from dba_scheduler_job_run_details where job_name like 'ORA$AT_OS_OPT_S%' order by 4;
11g版本查询结果类似如下：
OWNER JOB_NAME STATUS ACTUAL_START_DATE RUN_DURATION
------------------------------ ------------------------------ ------------------------------ ---------------------------------------- ------------------------------
SYS ORA$AT_OS_OPT_SY_3926 SUCCEEDED 22-NOV-17 10.00.02.384206 PM EST5EDT +000 00:01:41
SYS ORA$AT_OS_OPT_SY_3946 SUCCEEDED 23-NOV-17 10.00.02.078143 PM EST5EDT +000 00:01:54
SYS ORA$AT_OS_OPT_SY_3966 SUCCEEDED 24-NOV-17 10.00.02.684644 PM EST5EDT +000 00:02:03
SYS ORA$AT_OS_OPT_SY_3986 SUCCEEDED 25-NOV-17 06.00.02.592675 AM EST5EDT +000 00:01:54
SYS ORA$AT_OS_OPT_SY_4006 SUCCEEDED 25-NOV-17 10.02.37.976591 AM EST5EDT +000 00:00:39
SYS ORA$AT_OS_OPT_SY_4026 SUCCEEDED 25-NOV-17 02.02.55.191309 PM EST5EDT +000 00:00:36
SYS ORA$AT_OS_OPT_SY_4046 SUCCEEDED 25-NOV-17 06.03.08.913991 PM EST5EDT +000 00:00:36
SYS ORA$AT_OS_OPT_SY_4066 SUCCEEDED 25-NOV-17 10.03.22.624319 PM EST5EDT +000 00:01:12
SYS ORA$AT_OS_OPT_SY_4086 SUCCEEDED 26-NOV-17 06.00.08.274082 AM EST5EDT +000 00:01:14
SYS ORA$AT_OS_OPT_SY_4106 SUCCEEDED 26-NOV-17 10.04.06.172856 AM EST5EDT +000 00:00:46
SYS ORA$AT_OS_OPT_SY_4126 SUCCEEDED 26-NOV-17 02.04.23.754379 PM EST5EDT +000 00:01:04
SYS ORA$AT_OS_OPT_SY_4146 SUCCEEDED 26-NOV-17 06.04.40.989803 PM EST5EDT +000 00:00:54
SYS ORA$AT_OS_OPT_SY_4166 SUCCEEDED 26-NOV-17 10.04.55.633700 PM EST5EDT +000 00:00:56
SYS ORA$AT_OS_OPT_SY_4186 SUCCEEDED 27-NOV-17 10.00.08.203510 PM EST5EDT +000 00:02:25
SYS ORA$AT_OS_OPT_SY_4206 SUCCEEDED 28-NOV-17 10.00.01.365122 PM EST5EDT +000 00:02:16
SYS ORA$AT_OS_OPT_SY_4226 SUCCEEDED 29-NOV-17 11.05.57.084541 PM EST5EDT +000 00:01:58
可以看到，以统计信息收集的JOB_NAME为例，11g版本之后不再是固定的一个名字，而是以ORA$AT_OS_OPT_SY开头的命名。