RMAN> show  ARCHIVELOG DELETION POLICY ;

RMAN configuration parameters for database with db_unique_name ORCL are:
CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default

SQL> set linesize 200;
 select * from v$flash_recovery_area_usage where FILE_TYPE='ARCHIVED LOG';

FILE_TYPE		PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES	 CON_ID
----------------------- ------------------ ------------------------- --------------- ----------
ARCHIVED LOG			     12.27			   0		  21	      0

重新设置archivelog的删除策略

RMAN> CONFIGURE ARCHIVELOG DELETION POLICY TO SHIPPED TO ALL STANDBY;


SQL> set linesize 200;
 select * from v$flash_recovery_area_usage where FILE_TYPE='ARCHIVED LOG';
SQL> 
FILE_TYPE		PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE NUMBER_OF_FILES	 CON_ID
----------------------- ------------------ ------------------------- --------------- ----------
ARCHIVED LOG			     12.27		       12.27		  21	      0

我们可以看到随着我们改变归档日志的删除策略PERCENT_SPACE_RECLAIMABLE这个字段从0变成了12.27%。
需要说明的是可以被自动删除的归档日志不会在 report obsolete中报告。
下面的sql可以查询所有在备库上应用的归档日志：

select a.thread#, a.sequence#, a.applied from v$archived_log a, v$database d
where a.activation# = d.activation# and a.applied='YES';

如果在中有FRA,空间压力，这些日志将被自动删除，在数据库的alert.log 从将会看到类似下面的提示：

Deleted Oracle managed file /opt/app/oracle/FRA/<DB_NAME>/archivelog/2020_05_30/o1_mf_1_151_6y71q675_.arc
Deleted Oracle managed file /opt/app/oracle/FRA/<DB_NAME>/archivelog/2020_05_31/o1_mf_1_151_6y87pzg4_.arc