12c rman optimization优化设置失效？

实验过程

RMAN> show all;

RMAN configuration parameters for database with db_unique_name ORCL are:
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
CONFIGURE BACKUP OPTIMIZATION ON;
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '%F'; # default
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE MAXSETSIZE TO UNLIMITED; # default
CONFIGURE ENCRYPTION FOR DATABASE OFF; # default
CONFIGURE ENCRYPTION ALGORITHM 'AES128'; # default
CONFIGURE COMPRESSION ALGORITHM 'BASIC' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE ; # default
CONFIGURE RMAN OUTPUT TO KEEP FOR 7 DAYS; # default
CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/app/oracle/product/12.1.0/dbhome_1/dbs/snapcf_orcl.f'; # default

RMAN> backup archivelog from time 'sysdate-1/12' format '/home/oracle/arch_%d_%t_%s.bak';

Starting backup at 02-DEC-2017 16:04:04
current log archived
using channel ORA_DISK_1
channel ORA_DISK_1: starting archived log backup set
channel ORA_DISK_1: specifying archived log(s) in backup set
input archived log thread=1 sequence=296 RECID=562 STAMP=961687168
input archived log thread=1 sequence=297 RECID=563 STAMP=961687503
input archived log thread=1 sequence=298 RECID=568 STAMP=961687506
input archived log thread=1 sequence=299 RECID=570 STAMP=961688188
input archived log thread=1 sequence=300 RECID=572 STAMP=961688197
input archived log thread=1 sequence=301 RECID=574 STAMP=961688200
input archived log thread=1 sequence=302 RECID=576 STAMP=961688200
input archived log thread=1 sequence=303 RECID=578 STAMP=961688204
input archived log thread=1 sequence=304 RECID=580 STAMP=961688205
input archived log thread=1 sequence=305 RECID=582 STAMP=961688207
input archived log thread=1 sequence=306 RECID=584 STAMP=961688208
input archived log thread=1 sequence=307 RECID=586 STAMP=961688210
input archived log thread=1 sequence=308 RECID=588 STAMP=961688211
input archived log thread=1 sequence=309 RECID=590 STAMP=961688214
input archived log thread=1 sequence=310 RECID=592 STAMP=961688214
input archived log thread=1 sequence=311 RECID=594 STAMP=961688216
input archived log thread=1 sequence=312 RECID=596 STAMP=961689040
input archived log thread=1 sequence=313 RECID=598 STAMP=961689042
input archived log thread=1 sequence=314 RECID=600 STAMP=961689088
input archived log thread=1 sequence=315 RECID=602 STAMP=961689127
input archived log thread=1 sequence=316 RECID=604 STAMP=961689169
input archived log thread=1 sequence=317 RECID=606 STAMP=961689323
input archived log thread=1 sequence=318 RECID=608 STAMP=961689498
input archived log thread=1 sequence=319 RECID=610 STAMP=961689541
input archived log thread=1 sequence=320 RECID=612 STAMP=961689844
channel ORA_DISK_1: starting piece 1 at 02-DEC-2017 16:04:04
channel ORA_DISK_1: finished piece 1 at 02-DEC-2017 16:04:05
piece handle=/home/oracle/arch_ORCL_961689844_14.bak tag=TAG20171202T160404 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 02-DEC-2017 16:04:05

RMAN> 

RMAN> backup archivelog all format '/home/oracle/arch_%d_%t_%s.bak';

Starting backup at 02-DEC-2017 16:04:16
current log archived
using channel ORA_DISK_1
skipping archived logs of thread 1 from sequence 227 to 320; already backed up
channel ORA_DISK_1: starting archived log backup set
channel ORA_DISK_1: specifying archived log(s) in backup set
input archived log thread=1 sequence=321 RECID=614 STAMP=961689856
channel ORA_DISK_1: starting piece 1 at 02-DEC-2017 16:04:17
channel ORA_DISK_1: finished piece 1 at 02-DEC-2017 16:04:18
piece handle=/home/oracle/arch_ORCL_961689857_15.bak tag=TAG20171202T160416 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 02-DEC-2017 16:04:18

RMAN> list backup of archivelog all;

List of Backup Sets
===================
...省略...

BS Key  Size       Device Type Elapsed Time Completion Time     
------- ---------- ----------- ------------ --------------------
7       4.16M      DISK        00:00:00     02-DEC-2017 16:04:04
        BP Key: 7   Status: AVAILABLE  Compressed: NO  Tag: TAG20171202T160404
        Piece Name: /home/oracle/arch_ORCL_961689844_14.bak

  List of Archived Logs in backup set 7
  Thrd Seq     Low SCN    Low Time             Next SCN   Next Time
  ---- ------- ---------- -------------------- ---------- ---------
  1    296     4684573    02-DEC-2017 12:37:57 4684632    02-DEC-2017 15:19:28
  1    297     4684632    02-DEC-2017 15:19:28 4686128    02-DEC-2017 15:25:01
  1    298     4686128    02-DEC-2017 15:25:01 4686147    02-DEC-2017 15:25:06
  1    299     4686147    02-DEC-2017 15:25:06 4688091    02-DEC-2017 15:36:27
  1    300     4688091    02-DEC-2017 15:36:27 4688113    02-DEC-2017 15:36:36
  1    301     4688113    02-DEC-2017 15:36:36 4688123    02-DEC-2017 15:36:40
  1    302     4688123    02-DEC-2017 15:36:40 4688129    02-DEC-2017 15:36:40
  1    303     4688129    02-DEC-2017 15:36:40 4688142    02-DEC-2017 15:36:44
  1    304     4688142    02-DEC-2017 15:36:44 4688146    02-DEC-2017 15:36:44
  1    305     4688146    02-DEC-2017 15:36:44 4688156    02-DEC-2017 15:36:47
  1    306     4688156    02-DEC-2017 15:36:47 4688160    02-DEC-2017 15:36:47
  1    307     4688160    02-DEC-2017 15:36:47 4688170    02-DEC-2017 15:36:50
  1    308     4688170    02-DEC-2017 15:36:50 4688174    02-DEC-2017 15:36:50
  1    309     4688174    02-DEC-2017 15:36:50 4688184    02-DEC-2017 15:36:53
  1    310     4688184    02-DEC-2017 15:36:53 4688188    02-DEC-2017 15:36:54
  1    311     4688188    02-DEC-2017 15:36:54 4688198    02-DEC-2017 15:36:56
  1    312     4688198    02-DEC-2017 15:36:56 4690007    02-DEC-2017 15:50:40
  1    313     4690007    02-DEC-2017 15:50:40 4690015    02-DEC-2017 15:50:42
  1    314     4690015    02-DEC-2017 15:50:42 4690116    02-DEC-2017 15:51:28
  1    315     4690116    02-DEC-2017 15:51:28 4690212    02-DEC-2017 15:52:07
  1    316     4690212    02-DEC-2017 15:52:07 4690327    02-DEC-2017 15:52:49
  1    317     4690327    02-DEC-2017 15:52:49 4690692    02-DEC-2017 15:55:22
  1    318     4690692    02-DEC-2017 15:55:22 4691069    02-DEC-2017 15:58:17
  1    319     4691069    02-DEC-2017 15:58:17 4691175    02-DEC-2017 15:59:01
  1    320     4691175    02-DEC-2017 15:59:01 4691859    02-DEC-2017 16:04:04

BS Key  Size       Device Type Elapsed Time Completion Time     
------- ---------- ----------- ------------ --------------------
8       106.00K    DISK        00:00:00     02-DEC-2017 16:04:17
        BP Key: 8   Status: AVAILABLE  Compressed: NO  Tag: TAG20171202T160416
        Piece Name: /home/oracle/arch_ORCL_961689857_15.bak

  List of Archived Logs in backup set 8
  Thrd Seq     Low SCN    Low Time             Next SCN   Next Time
  ---- ------- ---------- -------------------- ---------- ---------
  1    321     4691859    02-DEC-2017 16:04:04 4691982    02-DEC-2017 16:04:16

RMAN> 

小结：
当备份归档日志使用from time的时候，CONFIGURE BACKUP OPTIMIZATION ON; 设置失效。
当备份归档日志使用all的时候，CONFIGURE BACKUP OPTIMIZATION ON; 设置生效。