ORACLE 11G 如何修改 awr 的保留期限小于8天

Oracle Database 11g 默认具备一个系统定义的Moving Window Baseline，该基线对应于 AWR 保留期中的所有 AWR 数据。
仅可存在一个Moving Window Baseline。
系统定义的Moving Window Baseline认大小为当前的AWR保留期，即默认为八天。

如果要增大Moving Window Baseline，首先需要相应增大AWR保留期。
AWR保留期和系统定义的Moving Window Baseline的大小是两个独立的参数。
但是AWR保留期必须大于或等于系统定义的Moving Window Baseline的大小。

-----------查看awr 的保留时间，快照间隔：

SQL> select DBID, SNAP_INTERVAL, SNAPINT_NUM, RETENTION from wrm$_wr_control;

   DBID     SNAP_INTERVAL            SNAPINT_NUM    RETENTION
---------- -------------------------------------------- -----------
4215476630 +00000 01:00:00.0           3600        +00030 00:00:00.0

SQL> select * from dba_hist_wr_control;

      DBID SNAP_INTERVAL                                                               RETENTION                                                                   TOPNSQL
---------- --------------------------------------------------------------------------- --------------------------------------------------------------------------- ----------
4215476630 +00000 01:00:00.0                                                           +00030 00:00:00.0                                                           DEFAULT

SQL>  select dbms_stats.get_stats_history_retention from dual;

GET_STATS_HISTORY_RETENTION
---------------------------
                         31

---------直接修改awr 保留期限为7天

SQL> exec dbms_workload_repository.modify_snapshot_settings(interval=>60, retention=>10080);
BEGIN dbms_workload_repository.modify_snapshot_settings(interval=>60, retention=>10080); END;

*
ERROR at line 1:
ORA-13541: system moving window baseline size (691200) greater than retention (604800)
ORA-06512: at "SYS.DBMS_WORKLOAD_REPOSITORY", line 174
ORA-06512: at "SYS.DBMS_WORKLOAD_REPOSITORY", line 222
ORA-06512: at line 1

10080=7*24*60*60
691200=8*24*60*60  8天

------------查看当前Moving Window Baseline的值

SQL> col BASELINE_NAME for a30
SQL> select dbid, baseline_name, baseline_type, moving_window_size from dba_hist_baseline;
      DBID BASELINE_NAME                  BASELINE_TYPE MOVING_WINDOW_SIZE
---------- ------------------------------ ------------- ------------------
4215476630 SYSTEM_MOVING_WINDOW           MOVING_WINDOW                  8

既然知道了原因，解决就很方便了，Modifying the Window Size of the Default Moving Window Baseline

BEGIN
    DBMS_WORKLOAD_REPOSITORY.MODIFY_BASELINE_WINDOW_SIZE (
                   window_size => 5,
                   dbid => 4215476630);
END;
/

其中要注意：window size必须设置为一个小于或等于AWR设置的保留值。

这时就可以修改awr 快照的保留时间了：

SQL> exec dbms_workload_repository.modify_snapshot_settings(interval=>60, retention=>10080);

PL/SQL procedure successfully completed.

SQL> select * from dba_hist_wr_control;

      DBID SNAP_INTERVAL                                                               RETENTION                                                                   TOPNSQL
---------- --------------------------------------------------------------------------- --------------------------------------------------------------------------- ----------
4215476630 +00000 01:00:00.0                                                           +00007 00:00:00.0                                                           DEFAULT