1）查询非当前的联机重做日志文件

sys@ORCL> select group#,sequence#,status,members from v$log;

    GROUP#  SEQUENCE# STATUS              MEMBERS
---------- ---------- ---------------- ----------
         1          7 INACTIVE                  2
         2          8 INACTIVE                  2
         3          9 CURRENT                   2

sys@ORCL> col member for a70 trunc
sys@ORCL> select group#,member from v$logfile where group#=2;

    GROUP# MEMBER
---------- ----------------------------------------------------------------------
         2 /u01/app/oracle/oradata/ORCL/onlinelog/o1_mf_2_8050hm84_.log
         2 /u01/app/oracle/flash_recovery_area/ORCL/onlinelog/o1_mf_2_8050ho5o_.l

    2）模拟文件丢失

sys@ORCL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
sys@ORCL> host rm /u01/app/oracle/oradata/ORCL/onlinelog/o1_mf_2_8050hm84_.log
sys@ORCL> host rm -rf /u01/app/oracle/flash_recovery_area/ORCL/onlinelog/o1_mf_2_8050ho5o_.log

sys@ORCL> startup
ORACLE instance started.

Total System Global Area  419430400 bytes
Fixed Size                  1219760 bytes
Variable Size             159384400 bytes
Database Buffers          255852544 bytes
Redo Buffers                2973696 bytes
Database mounted.
ORA-00313: open failed for members of log group 2 of thread 1
ORA-00312: online log 2 thread 1: \'/u01/app/oracle/oradata/ORCL/onlinelog/o1_mf_2_8050hm84_.log\'
ORA-00312: online log 2 thread 1:
\'/u01/app/oracle/flash_recovery_area/ORCL/onlinelog/o1_mf_2_8050ho5o_.log\'

    3）修复丢失的联机重做日志文件

sys@ORCL> alter database clear logfile group 2;

Database altered.

sys@ORCL> alter database open;

Database altered.

sys@ORCL> col member for a72 wrapped
sys@ORCL> select group#,member from v$logfile where group#=2;

    GROUP# MEMBER
---------- ------------------------------------------------------------------------
         2 /u01/app/oracle/oradata/ORCL/onlinelog/o1_mf_2_8244vp4j_.log
         2 /u01/app/oracle/flash_recovery_area/ORCL/onlinelog/o1_mf_2_8244vttx_.log