今天遇到一个奇怪的事情，使用OBSOLETE不删除归档日志，而且也不删除过期的归档的BACKUP SET
从delete obsolete的概念来看如下：
The REPORT OBSOLETE and DELETE OBSOLETE commands work in two steps:
For each datafile for which there are full backup, datafile copy, or level 0 incremental backups, RMAN identifies the oldest full or
level 0 backup or copy that is not obsolete under the retention policy being tested. Any full backup, level 0 incremental backup, or
datafile copy of a datafile older than the one identified in this step is considered obsolete. Rman Not Deleting Obsolete Archive Logs And Archive Log Backups (文档 ID 282617.1)
Any archived logs and level 1 incremental backups that are older than the oldest non-obsolete full backup are then obsolete because
there is no full or level 0 backup to which they can be applied.
可以看到所谓的冗余策略不管是天数还是副本数量，保证的都是你冗余时间或者副本最早的那一个FULL BACKUP DATABASE（FULL BACK 或者LEVEL 0增量备份）
是能够恢复的，而早于这个FULL BACKUP以前的增量备份和归档日志或者其他备份都是失效的。简单的说delete obsolete会删除已经没有用的不用于恢复的
归档日志。但是今天遇到的问题是明显的已经处于无用状态的归档任然保留，delete obsolete不能删除。
查看MOS发现问题如下：
once the datafile is identified, the file must be brought up to date with the other files. To do this, execute the following steps:
# If file is Offline:
1. Recover datafile XX:
alter database recover datafile XX
-- recovery will apply archives.
2. Set the Datafile Online
alter database datafile XX online;
or
# If tablespace is in begin backup mode:
1. sql> alter tablespace end backup;
Once file is brought upto date, RMAN will not have the need to retain older archivelog files.
简单的说就是如果有数据文件处于OFFLINE 状态或者HOT BACKUP 状态，一旦重新ONLINE这个数据文件或者END BACKUP这个文件
是需要归档来进行恢复，所以是不能删除的，所以马上查看数据文件状态如下：
查询过程和处理过程
SQL> select * from dba_data_files;
FILE_NAME ONLINE_STATUS
-------------------------------------------------------- -------------
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\USERS01.DBF ONLINE
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\SYSAUX01.DBF ONLINE
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\UNDOTBS01.DBF ONLINE
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\SYSTEM01.DBF SYSTEM
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\TEST01.DBF ONLINE
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\UNTDOTBS01.DBF ONLINE
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\TESTCK.DBF RECOVER
7 rows selected
SQL> drop tablespace testck;
drop tablespace testck
ORA-01549: tablespace not empty, use INCLUDING CONTENTS option
SQL> drop tablespace testck including contents and datafiles;
Tablespace dropped
SQL> select * from dba_data_files;
FILE_NAME ONLINE_STATUS
-------------------------------------------------------- -------------
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\USERS01.DBF ONLINE
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\SYSAUX01.DBF ONLINE
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\UNDOTBS01.DBF ONLINE
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\SYSTEM01.DBF SYSTEM
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\TEST01.DBF ONLINE
C:\ORACLE\PRODUCT\10.2.0\ORADATA\BENDI\UNTDOTBS01.DBF ONLINE
6 rows selected
我删除了表空间后，REPORT OBSOLETE可以正常删除过期的归档和归档备份集。
当然也有MOS文章说还有一种可能的情况就是BUG。
Bug 12412131 - Archivelog backups are not being deleted by 'DELETE OBSOLETE' (文档 ID 12412131.8)