只要你查询v$logfile，redo log以及standby redo log路径正确：
1.你可以在为开启dg同步之前手工执行ALTER DATABASE CLEAR LOGFILE GROUP x;生成物理上对应的文件。
2.或者你无需执行，会在你开启恢复的时候，oracle自动完成clear生成物理对应文件，这个过程可以从alert日志中看到。
例如下面就是第二种情况的示例：

ALTER DATABASE RECOVER  managed standby database disconnect from session  
Attempt to start background Managed Standby Recovery process (honordg)
Tue Feb 02 01:59:20 2021
MRP0 started with pid=20, OS id=45884 
MRP0: Background Managed Standby Recovery process started (honordg)
Serial Media Recovery started
Managed Standby Recovery not using Real Time Apply
Waiting for all non-current ORLs to be archived...
All non-current ORLs have been archived.
Errors in file /oracle/app/oracle/diag/rdbms/honordg/honordg/trace/honordg_mrp0_45884.trc:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: '+DATADG/honor/onlinelog/group_1.261.984508005'
ORA-17503: ksfdopn:2 Failed to open file +DATADG/honor/onlinelog/group_1.261.984508005
ORA-15001: diskgroup "DATADG" does not exist or is not mounted
ORA-15077: could not locate ASM instance serving a required diskgroup
Clearing online redo logfile 1 +DATADG/honor/onlinelog/group_1.261.984508005
Clearing online log 1 of thread 1 sequence number 1748