12c Cannot Start Database Due to Flashback Enabled

ASMCMD [+datadg/orcl] > cd flashback
ASMCMD [+datadg/orcl/flashback] > ls
log_1.377.964637895
log_2.376.964637901
log_3.374.964648865
ASMCMD [+datadg/orcl/flashback] > rm log_*
ASMCMD [+datadg/orcl/flashback] >

SYS@orcl1> startup
ORACLE instance started.

Total System Global Area 1241513984 bytes
Fixed Size                  2923872 bytes
Variable Size             620757664 bytes
Database Buffers          603979776 bytes
Redo Buffers               13852672 bytes
Database mounted.
ORA-38760: This database instance failed to turn on flashback database

3、日志报错
SYS@orcl1>

RVWR started with pid=40, OS id=10323
Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl1/trace/orcl1_rvwr_10323.trc:
ORA-38701: Flashback database log 2 seq 2 thread 1: "+DATADG/ORCL/FLASHBACK/log_2.376.964637901"
ORA-17503: ksfdopn:2 Failed to open file +DATADG/ORCL/FLASHBACK/log_2.376.964637901
ORA-15012: ASM file '+DATADG/ORCL/FLASHBACK/log_2.376.964637901' does not exist
Database mounted in Shared Mode (CLUSTER_DATABASE=TRUE)
Lost write protection disabled
Completed: ALTER DATABASE   MOUNT
ALTER DATABASE OPEN
Errors in file /u01/app/oracle/diag/rdbms/orcl/orcl1/trace/orcl1_ora_10324.trc:
ORA-38760: This database instance failed to turn on flashback database
ORA-38760 signalled during: ALTER DATABASE OPEN...
2018-01-06 07:57:34.698000 +08:00
Decreasing number of real time LMS from 1 to 0

SYS@orcl1>
SYS@orcl1> alter database flashback off;

Database altered.

SYS@orcl1> alter database open;

Database altered.

SYS@orcl1> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SYS@orcl1> startup mount;
ORACLE instance started.

Total System Global Area 1241513984 bytes
Fixed Size                  2923872 bytes
Variable Size             620757664 bytes
Database Buffers          603979776 bytes
Redo Buffers               13852672 bytes
Database mounted.
SYS@orcl1> alter database flashback on;

Database altered.

SYS@orcl1> alter database open;

Database altered.

SYS@orcl1> select flashback_on from v$database;

FLASHBACK_ON
------------------
YES

SYS@orcl1>