最近在验证、测试备份有效性时，遇到了“ORA-01180: can not create datafile 1”这个错误，顺便结合metalink的官方文档“RMAN restore fails with ORA-01180: can not create datafile 1 (文档 ID 1265151.1)”里面的内容做一个学习、归纳、总结，顺便加深一下理解。
creating datafile fno=1 name=/u01/oradata/SCM2/system01.dbf
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 06/14/2018 10:28:34
ORA-01180: can not create datafile 1
ORA-01110: data file 1: '/u01/oradata/SCM2/system01.dbf'
当然这个数据文件可能是system01.dbf,也可能是其它任何数据文件。但是如果它是FILE_ID为1数据文件，那么就是关键问题，因为FILE_ID为1是系统数据文件。它无法在RMAN还原过程中被创建。而它又必须从备份中还原（restore）。出现这个错误呢，要么就是没有可用的备份（no backups available for use），要么是当前的化身（Incarnation） 未正确设置。
官方文档提供下面命令来判别具体原因.
RMAN> list incarnation of database;
RMAN> list backup of datafile 1;
RMAN> list copy of datafile 1;
RMAN> list backup summary;
1: 检查是否没有可用的备份
如下命令所示，你可以检查是否存在可用的备份
RMAN> list backup of datafile 1;
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
21778 Full 2.47G DISK 00:08:28 03-JUN-18
BP Key: 21778 Status: EXPIRED Compressed: YES Tag: TAG20180603T002006
Piece Name: /u04/backup/backupsets/ora_df977790007_s23771_s1
List of Datafiles in backup set 21778
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 28945050985 03-JUN-18 /u01/oradata/SCM2/system01.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
21792 Full 2.47G DISK 00:08:21 04-JUN-18
BP Key: 21792 Status: EXPIRED Compressed: YES Tag: TAG20180604T001936
Piece Name: /u04/backup/backupsets/ora_df977876376_s23786_s1
List of Datafiles in backup set 21792
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 28945603859 04-JUN-18 /u01/oradata/SCM2/system01.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
21806 Full 2.47G DISK 00:08:33 05-JUN-18
BP Key: 21806 Status: AVAILABLE Compressed: YES Tag: TAG20180605T002025
Piece Name: /u04/backup/backupsets/ora_df977962825_s23801_s1
List of Datafiles in backup set 21806
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 28946703480 05-JUN-18 /u01/oradata/SCM2/system01.dbf
RMAN>
如上所示，虽然有两个备份文件状态是EXPIRED，但是还是存在一个可用的备份文件，如果备份的状态全部是EXPIRED，则对备份集键运行crosscheck 查看它是否存在，例如
RMAN> crosscheck backupset 138;
如果存在，状态将会被更新为AVAILABLE。如果在运行crosscheck后状态仍为EXPIRED，则你需要的备份在物理上不存在。
RMAN> crosscheck backupset 21806;
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=910 devtype=DISK
crosschecked backup piece: found to be 'AVAILABLE'
backup piece handle=/u04/backup/backupsets/ora_df977962825_s23801_s1 recid=21806 stamp=977962827
Crosschecked 1 objects
RMAN> crosscheck backupset 21804;
using channel ORA_DISK_1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of crosscheck command at 06/15/2018 08:21:59
RMAN-06160: no backup pieces found for backup set key: 21804
RMAN>
$ ls /u04/backup/backupsets/ora_df977876376_s23786_s1
ls: /u04/backup/backupsets/ora_df977876376_s23786_s1: No such file or directory
$ ls /u04/backup/backupsets/ora_df977790007_s23771_s1
ls: /u04/backup/backupsets/ora_df977790007_s23771_s1: No such file or directory
$ ls /u04/backup/backupsets/ora_df977962825_s23801_s1
/u04/backup/backupsets/ora_df977962825_s23801_s1
$
2： 检查数据库当前的Incarnation
官方文档提供的例子如下所示
RMAN> list backup of datafile 1;
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ --------------------
138 Full 531.25M DISK 00:00:00 13 FEB 2015 14:31:35
BP Key: 136 Status: AVAILABLE Compressed: NO Tag: TAG20150213T143135
Piece Name: /opt/app/oracle/fra/ORA102/backupset/2015_02_13/o1_mf_nnndf_TAG20150213T143135_bftw0r14_.bkp
List of Datafiles in backup set 138
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- -------------------- ----
1 Full 25207062 13 FEB 2015 14:31:35 /opt/app/oracle/oradata/ORA102/system01.dbf
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ --------------------
139 Full 531.32M DISK 00:00:00 13 FEB 2015 14:09:34
BP Key: 137 Status: AVAILABLE Compressed: NO Tag: TAG20150213T140934
Piece Name: /opt/app/oracle/fra/ORA102/backupset/2015_02_13/o1_mf_nnndf_TAG20150213T140934_bfttqhh6_.bkp
List of Datafiles in backup set 139
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- -------------------- ----
1 Full 25206825 13 FEB 2015 14:09:34 /opt/app/oracle/oradata/ORA102/system01.dbf
RMAN> list incarnation of database;
List of Database Incarnations
DB Key Inc Key DB Name DB ID STATUS Reset SCN Reset Time
------- ------- -------- ---------------- --- ---------- ----------
1 1 ORA102 400119926 CURRENT 1 19 MAR 2012 15:29:58
2 2 ORA102 400119926 ORPHAN 5766931 04 OCT 2012 15:37:51
3 3 ORA102 400119926 ORPHAN 5768164 16 OCT 2012 15:33:09
...
9 9 ORA102 400119926 ORPHAN 25204629 13 FEB 2015 13:03:55
10 10 ORA102 400119926 ORPHAN 25205038 13 FEB 2015 13:35:57
11 11 ORA102 400119926 ORPHAN 25206695 13 FEB 2015 14:09:07
13 13 ORA102 400119926 ORPHAN 25206882 13 FEB 2015 14:16:24
14 14 ORA102 400119926 ORPHAN 25206882 13 FEB 2015 14:43:32
12 12 ORA102 400119926 ORPHAN 25206883 13 FEB 2015 14:30:54
要还原在2015年2月13日14点09分34秒进行的备份标签 (TAG20150213T140934)，你必须在执行还原之前将incarnation重置为11 。
RMAN> reset database to incarnation 11;
个人遇到的例子如下，使用Tag为TAG20180605T002025的备份集还原，照理说当前的Incarnation是正确的
RMAN> list backup of datafile 1;
using target database control file instead of recovery catalog
List of Backup Sets
===================
BS Key Type LV Size Device Type Elapsed Time Completion Time
------- ---- -- ---------- ----------- ------------ ---------------
21806 Full 2.47G DISK 00:08:33 05-JUN-18
BP Key: 21806 Status: AVAILABLE Compressed: YES Tag: TAG20180605T002025
Piece Name: /u04/backup/backupsets/ora_df977962825_s23801_s1
List of Datafiles in backup set 21806
File LV Type Ckp SCN Ckp Time Name
---- -- ---- ---------- --------- ----
1 Full 28946703480 05-JUN-18 /u01/oradata/SCM2/system01.dbf
RMAN> list incarnation of database;
List of Database Incarnations
DB Key Inc Key DB Name DB ID STATUS Reset SCN Reset Time
------- ------- -------- ---------------- --- ---------- ----------
1 1 SCM2 4095319980 PARENT 1 05-OCT-12
2 2 SCM2 4095319980 CURRENT 28333829966 28-MAR-18
那么，我们检查一下告警日志，如下截图所示，因为catalog归档日志时，把不相关的归档日志catalog了，Oracle从归档日志中自动探测到incarnation信息，并重置incarnation，从而导致恢复报错。
参考官方文档 RMAN restore database fails ORA-01180: can not create datafile 1 (文档 ID 1573040.1)
When a BACKUP controlfile is used with a Flash Recovery Area defined, an implicit crosscheck of the FRA is done and any files found belonging to the database are catalog'd to the controlfile.
Archivelogs created after a resetlogs operation will cause a new incarnation to be registered in the controlfile.
The new incarnations meant the database backup needed for restore no longer belonged to the current incarnation.
参考资料：
RMAN restore fails with ORA-01180: can not create datafile 1 (文档 ID 1265151.1)
RMAN restore database fails ORA-01180: can not create datafile 1 (文档 ID 1573040.1)