delete obsolete 是把旧于备份保留策略定义的备份数据同时也更新RMAN资料库以及控制文件，同时也应用于数据文件、控制文件、也有控制文件，是通过CONFIGURE RETENTION POLICY 来定义的策略的。
经过测试发现，delete noprompt obsolete;只会根据RMAN的保留策略为参考，如果在T0时间点存在多个归档日志，在T1时间点做了RMAN全备，此时report obsolete；那么T0时间点的归档日志都会被标记为过期，再根据保留策略RMAN会清理归档日志。
所以，针对Primary需要保存最近的archivelog，以便standby出现archivelog gap时过来取，或者有部署goldengate，需要至少保留3天的归档时，最好不要用delete noprompt obsolete; 这个命令。
以下是测试过程：
1、切多次日志
SQL> alter system switch logfile;
System altered.
SQL> alter system switch logfile;
System altered.
SQL> alter system switch logfile;
System altered.
SQL> alter system switch logfile;
System altered.
2、查看归档日志文件
[root@single19c 2022_09_01]# ls -lrt
total 35524
-rw-r----- 1 oracle oinstall 3851264 Sep 1 23:17 o1_mf_1_37_kk1m7pf5_.arc
-rw-r----- 1 oracle oinstall 32485376 Sep 1 23:19 o1_mf_1_38_kk1md7sh_.arc
-rw-r----- 1 oracle oinstall 2048 Sep 1 23:19 o1_mf_1_39_kk1mdc4c_.arc
-rw-r----- 1 oracle oinstall 28672 Sep 1 23:19 o1_mf_1_40_kk1mdglx_.arc
-rw-r----- 1 oracle oinstall 2048 Sep 1 23:19 o1_mf_1_41_kk1mdjot_.arc
3、RMAN 全备
[oracle@single19c ~]$ rman target /
Recovery Manager: Release 19.0.0.0.0 - Production on Thu Sep 1 23:21:45 2022
Version 19.16.0.0.0
Copyright (c) 1982, 2019, Oracle and/or its affiliates. All rights reserved.
connected to target database: S19C (DBID=560979251)
RMAN> backup database format '/u01/backup/full_db_%U_%T.ba' tag=full_db;
Starting backup at 01-SEP-22
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=65 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00001 name=/u01/app/oradata/S19C/system01.dbf
input datafile file number=00003 name=/u01/app/oradata/S19C/sysaux01.dbf
input datafile file number=00004 name=/u01/app/oradata/S19C/undotbs01.dbf
input datafile file number=00007 name=/u01/app/oradata/S19C/users01.dbf
channel ORA_DISK_1: starting piece 1 at 01-SEP-22
channel ORA_DISK_1: finished piece 1 at 01-SEP-22
piece handle=/u01/backup/full_db_0416kbuc_4_1_1_20220901.ba tag=FULL_DB comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:35
Finished backup at 01-SEP-22
Starting Control File and SPFILE Autobackup at 01-SEP-22
piece handle=/u01/arch/S19C/autobackup/2022_09_01/o1_mf_s_1114255344_kk09cjrg_.bkp comment=NONE
Finished Control File and SPFILE Autobackup at 01-SEP-22
RMAN> list backup;
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
1 Full 10.20M DISK 00:00:00 24-AUG-22
BP Key: 1 Status: AVAILABLE Compressed: NO Tag: TAG20220824T221301
Piece Name: /u01/arch/S19C/autobackup/2022_08_24/o1_mf_s_1113603181_kjddhfw5_.bkp
SPFILE Included: Modification time: 24-AUG-22
SPFILE db_unique_name: S19C
Control File Included: Ckp SCN: 2430579 Ckp time: 24-AUG-22
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
2 Full 10.17M DISK 00:00:01 24-AUG-22
BP Key: 2 Status: AVAILABLE Compressed: NO Tag: TAG20220824T223427
Piece Name: /u01/app/oradata/S19C/standby_02160gbj_2_1_1.ctl
Standby Control File Included: Ckp SCN: 2434188 Ckp time: 24-AUG-22
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
3 Full 10.20M DISK 00:00:00 24-AUG-22
BP Key: 3 Status: AVAILABLE Compressed: NO Tag: TAG20220824T223429
Piece Name: /u01/arch/S19C/autobackup/2022_08_24/o1_mf_s_1113604469_kjdfqot9_.bkp
SPFILE Included: Modification time: 24-AUG-22
SPFILE db_unique_name: S19C
Control File Included: Ckp SCN: 2434200 Ckp time: 24-AUG-22
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
4 Full 1.48G DISK 00:00:32 01-SEP-22
BP Key: 4 Status: AVAILABLE Compressed: NO Tag: FULL_DB
Piece Name: /u01/backup/full_db_0416kbuc_4_1_1_20220901.ba
List of Datafiles in backup set 4
File LV Type Ckp SCN Ckp Time Abs Fuz SCN Sparse Name
---- -- ---- ---------- --------- ----------- ------ ----
1 Full 3038848 01-SEP-22 NO /u01/app/oradata/S19C/system01.dbf
3 Full 3038848 01-SEP-22 NO /u01/app/oradata/S19C/sysaux01.dbf
4 Full 3038848 01-SEP-22 NO /u01/app/oradata/S19C/undotbs01.dbf
7 Full 3038848 01-SEP-22 NO /u01/app/oradata/S19C/users01.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
5 Full 10.23M DISK 00:00:00 01-SEP-22
BP Key: 5 Status: AVAILABLE Compressed: NO Tag: TAG20220901T112224
Piece Name: /u01/arch/S19C/autobackup/2022_09_01/o1_mf_s_1114255344_kk09cjrg_.bkp
SPFILE Included: Modification time: 01-SEP-22
SPFILE db_unique_name: S19C
Control File Included: Ckp SCN: 3038927 Ckp time: 01-SEP-22
4、查看过期备份
RMAN> report obsolete;
RMAN retention policy will be applied to the command
RMAN retention policy is set to redundancy 1
Report of obsolete backups and copies
Type Key Completion Time Filename/Handle
-------------------- ------ ------------------ --------------------
Archive Log 1 24-AUG-22 /u01/arch/S19C/archivelog/2022_08_24/o1_mf_1_22_kjdcyzjs_.arc
Archive Log 2 24-AUG-22 /u01/arch/S19C/archivelog/2022_08_24/o1_mf_1_23_kjddv5dp_.arc
Backup Set 1 24-AUG-22
Backup Piece 1 24-AUG-22 /u01/arch/S19C/autobackup/2022_08_24/o1_mf_s_1113603181_kjddhfw5_.bkp
Archive Log 3 24-AUG-22 /u01/arch/S19C/archivelog/2022_08_24/o1_mf_1_24_kjddwfsn_.arc
Backup Set 2 24-AUG-22
Backup Piece 2 24-AUG-22 /u01/app/oradata/S19C/standby_02160gbj_2_1_1.ctl
Archive Log 4 24-AUG-22 /u01/arch/S19C/archivelog/2022_08_24/o1_mf_1_25_kjdgx8mm_.arc
Backup Set 3 24-AUG-22
Backup Piece 3 24-AUG-22 /u01/arch/S19C/autobackup/2022_08_24/o1_mf_s_1113604469_kjdfqot9_.bkp
Archive Log 6 25-AUG-22 /u01/arch/S19C/archivelog/2022_08_25/o1_mf_1_26_kjdp49wk_.arc
Archive Log 8 25-AUG-22 /u01/arch/S19C/archivelog/2022_08_25/o1_mf_1_27_kjf5snk1_.arc
Archive Log 10 25-AUG-22 /u01/arch/S19C/archivelog/2022_08_25/o1_mf_1_28_kjfgc7cw_.arc
Archive Log 12 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_29_kjjf267c_.arc
Archive Log 14 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_31_kjjlo1sx_.arc
Archive Log 15 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_30_kjjlnzsq_.arc
Archive Log 17 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_32_kjjlo3yl_.arc
Archive Log 20 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_33_kjjm25hy_.arc
Archive Log 22 27-AUG-22 /u01/arch/S19C/archivelog/2022_08_27/o1_mf_1_34_kjlv6m6l_.arc
Archive Log 24 27-AUG-22 /u01/arch/S19C/archivelog/2022_08_27/o1_mf_1_35_kjlvh45z_.arc
Archive Log 26 27-AUG-22 /u01/arch/S19C/archivelog/2022_08_27/o1_mf_1_36_kjlvh56j_.arc
Archive Log 28 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_37_kk1m7pf5_.arc
Archive Log 30 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_38_kk1md7sh_.arc
Archive Log 31 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_39_kk1mdc4c_.arc
Archive Log 34 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_40_kk1mdglx_.arc
Archive Log 36 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_41_kk1mdjot_.arc
做好全备之后，之前产生的归档日志都会标记为过期
5、删除过期备份
RMAN> delete obsolete;
RMAN retention policy will be applied to the command
RMAN retention policy is set to redundancy 1
using channel ORA_DISK_1
Deleting the following obsolete backups and copies:
Type Key Completion Time Filename/Handle
-------------------- ------ ------------------ --------------------
Archive Log 1 24-AUG-22 /u01/arch/S19C/archivelog/2022_08_24/o1_mf_1_22_kjdcyzjs_.arc
Archive Log 2 24-AUG-22 /u01/arch/S19C/archivelog/2022_08_24/o1_mf_1_23_kjddv5dp_.arc
Backup Set 1 24-AUG-22
Backup Piece 1 24-AUG-22 /u01/arch/S19C/autobackup/2022_08_24/o1_mf_s_1113603181_kjddhfw5_.bkp
Archive Log 3 24-AUG-22 /u01/arch/S19C/archivelog/2022_08_24/o1_mf_1_24_kjddwfsn_.arc
Backup Set 2 24-AUG-22
Backup Piece 2 24-AUG-22 /u01/app/oradata/S19C/standby_02160gbj_2_1_1.ctl
Archive Log 4 24-AUG-22 /u01/arch/S19C/archivelog/2022_08_24/o1_mf_1_25_kjdgx8mm_.arc
Backup Set 3 24-AUG-22
Backup Piece 3 24-AUG-22 /u01/arch/S19C/autobackup/2022_08_24/o1_mf_s_1113604469_kjdfqot9_.bkp
Archive Log 6 25-AUG-22 /u01/arch/S19C/archivelog/2022_08_25/o1_mf_1_26_kjdp49wk_.arc
Archive Log 8 25-AUG-22 /u01/arch/S19C/archivelog/2022_08_25/o1_mf_1_27_kjf5snk1_.arc
Archive Log 10 25-AUG-22 /u01/arch/S19C/archivelog/2022_08_25/o1_mf_1_28_kjfgc7cw_.arc
Archive Log 12 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_29_kjjf267c_.arc
Archive Log 14 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_31_kjjlo1sx_.arc
Archive Log 15 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_30_kjjlnzsq_.arc
Archive Log 17 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_32_kjjlo3yl_.arc
Archive Log 20 26-AUG-22 /u01/arch/S19C/archivelog/2022_08_26/o1_mf_1_33_kjjm25hy_.arc
Archive Log 22 27-AUG-22 /u01/arch/S19C/archivelog/2022_08_27/o1_mf_1_34_kjlv6m6l_.arc
Archive Log 24 27-AUG-22 /u01/arch/S19C/archivelog/2022_08_27/o1_mf_1_35_kjlvh45z_.arc
Archive Log 26 27-AUG-22 /u01/arch/S19C/archivelog/2022_08_27/o1_mf_1_36_kjlvh56j_.arc
Archive Log 28 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_37_kk1m7pf5_.arc
Archive Log 30 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_38_kk1md7sh_.arc
Archive Log 31 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_39_kk1mdc4c_.arc
Archive Log 34 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_40_kk1mdglx_.arc
Archive Log 36 01-SEP-22 /u01/arch/S19C/archivelog/2022_09_01/o1_mf_1_41_kk1mdjot_.arc
Do you really want to delete the above objects (enter YES or NO)? yes
6、再次查看归档日志
[root@single19c 2022_09_01]# ll -hrt
total 0
RMAN> list archivelog all;
specification does not match any archived log in the repository
总结：T1时间点做RMAN全备，做完全备之后在T1时间点之前的归档日志、增量备份、控制文件参数文件备份都会标记为过期
