错误描述：
RMAN> backup database plus archivelog;
Starting backup at 04-DEC-15
current log archived
using channel ORA_DISK_1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of backup plus archivelog command at 12/04/2015 16:59:43
RMAN-06059: expected archived log not found, loss of archived log compromises recoverability
ORA-19625: error identifying file /u2/oracle/fast_recovery_area/ORCL/archivelog/2015_11_01/o1_mf_1_242_c3cbn4fr_.arc
ORA-27037: unable to obtain file status
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3
原因：操作系统中删除了这个归档日志，日志还没备份过，rman备份时找不到这个归档就报错了。
解决方法：进行交叉检测
RMAN> change archivelog all crosscheck；
