Redo failure : Current Redo dropped

Alert log content :
==============

Errors in file /data01/app/oracle/diag/rdbms/orcl2/orcl2/trace/orcl2_ora_13908.trc:
ORA-00313: open failed for members of log group 1 of thread 
ORA-00312: online log 5 thread 1: '/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_5_cfxr8o6y_.log'
ORA-00312: online log 5 thread 1: '/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_5_cfxr8o9b_.log'
Tue Mar 08 09:36:39 2016
ARC1 started with pid=23, OS id=13922
Tue Mar 08 09:36:39 2016
ARC2 started with pid=24, OS id=13924
Tue Mar 08 09:36:39 2016

Identify the files which are not available :

SQL> select member, a.group#, a.status, a.archived  from v$log a, v$logfile b where  a.group# = b.group# order by a.group#, member;

MEMBER                                              GROUP#   STATUS         ARC
--------------------------------------------------------------------------- ---------- ---------------- ------- ------- ------- ------- ------- ---- ---- ---
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_1_cfxpjlf6_.log     1 INACTIVE YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_1_cfxpjl8v_.log                     1   INACTIVE YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_2_cfxpjnpd_.log     2   INACTIVE YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_2_cfxpjnms_.log              2   INACTIVE YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_3_cfxpjpo5_.log     3   INACTIVE YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_3_cfxpjpld_.log                     3   INACTIVE YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_4_cfxr8hlq_.log     4   INACTIVE YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_4_cfxr8hj4_.log                     4   INACTIVE YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_5_cfxr8o9b_.log     5   CURRENT NO
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_5_cfxr8o6y_.log             5   CURRENT NO
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_6_cfxr8rbl_.log     6 INACTIVE YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_6_cfxr8r86_.log                      6 INACTIVE YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_7_cfxr8vms_.log     7 INACTIVE YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_7_cfxr8vk7_.log              7 INACTIVE YES


Unfortunately, we have lost all members of a current online redo log group. Here are some possible options:

• Perform an incomplete recovery up to the last good SCN.
• If flashback is enabled, flash your database back to the last good SCN.
• If you’re using Oracle Data Guard, fail over to your physical or logical standby database.
• Contact Oracle Support for suggestions.

In our case we don't have falshback enabled . So we will perform incomplete recovery upto last good scn . 

So let's find the last good SCN : 

SQL> select group#, status, archived, thread#, sequence#, first_change# from v$log order by first_change# ;

    GROUP#   STATUS         ARC  THREAD#  SEQUENCE# FIRST_CHANGE#
---------- ---------------- --- ---------- ---------- ---------------- ---------------- ---------------- -------------
6           INACTIVE    YES 1             14            1733941 ------------> Safe
7           INACTIVE    YES 1             15             1733945 ------------> Safe
2           INACTIVE    YES 1             16             1733948  ------------> Safe
3           INACTIVE    YES 1             17             1733951  ------------> Safe
1           INACTIVE    YES 1             18             1733954  ------------> Safe
4           INACTIVE    YES 1             19             1733957  ------------> Safe
5           CURRENT    NO  1             20                1733960  ------------> Damaged 

So in our case we can recover the database until 1733960  .

[oracle@node2 2016_03_08]$ rman target /

Recovery Manager: Release 12.1.0.1.0 - Production on Tue Mar 8 09:41:29 2016

Copyright (c) 1982, 2013, Oracle and/or its affiliates.  All rights reserved.

connected to target database: ORCL2 (DBID=886768067, not open)

RMAN> restore database until sequence 1733960 ;

Starting restore at 20160308.094146
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=21 device type=DISK

channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00001 to /data01/app/oracle/oradata/ORCL2/datafile/o1_mf_system_cfxpdor9_.dbf
channel ORA_DISK_1: restoring datafile 00003 to /data01/app/oracle/oradata/ORCL2/datafile/o1_mf_sysaux_cfxpb0jb_.dbf
channel ORA_DISK_1: restoring datafile 00004 to /data01/app/oracle/oradata/ORCL2/datafile/o1_mf_undotbs1_cfxpj05f_.dbf
channel ORA_DISK_1: restoring datafile 00006 to /data01/app/oracle/oradata/ORCL2/datafile/o1_mf_users_cfxphz0d_.dbf
channel ORA_DISK_1: reading from backup piece /data01/app/oracle/fast_recovery_area/ORCL2/backupset/2016_03_08/o1_mf_nnndf_TAG20160308T092958_cfxrh744_.bkp
channel ORA_DISK_1: piece handle=/data01/app/oracle/fast_recovery_area/ORCL2/backupset/2016_03_08/o1_mf_nnndf_TAG20160308T092958_cfxrh744_.bkp tag=TAG20160308T092958
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:45
Finished restore at 20160308.094233

RMAN> recover database until sequence  1733960 ;

Starting recover at 20160308.094246
using channel ORA_DISK_1

starting media recovery

archived log for thread 1 with sequence 12 is already on disk as file /data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_12_cfxrk0ct_.arc
archived log for thread 1 with sequence 13 is already on disk as file /data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_13_cfxrl4z2_.arc
archived log for thread 1 with sequence 14 is already on disk as file /data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_14_cfxrlcwy_.arc
archived log for thread 1 with sequence 15 is already on disk as file /data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_15_cfxrlf01_.arc
archived log for thread 1 with sequence 16 is already on disk as file /data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_16_cfxrlfqz_.arc
archived log for thread 1 with sequence 17 is already on disk as file /data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_17_cfxrlggq_.arc
archived log for thread 1 with sequence 18 is already on disk as file /data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_18_cfxrlk6w_.arc
archived log for thread 1 with sequence 19 is already on disk as file /data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_19_cfxrln78_.arc
archived log file name=/data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_12_cfxrk0ct_.arc thread=1 sequence=12
archived log file name=/data01/app/oracle/fast_recovery_area/ORCL2/archivelog/2016_03_08/o1_mf_1_13_cfxrl4z2_.arc thread=1 sequence=13
media recovery complete, elapsed time: 00:00:01
Finished recover at 20160308.094248

RMAN> alter database open resetlogs;

Statement processed

SQL> select group#, status, archived, thread#, sequence#, first_change# from v$log;

    GROUP# STATUS           ARC    THREAD#  SEQUENCE# FIRST_CHANGE#
---------- ---------------- --- ---------- ---------- ----------------------------------------------------
1 CURRENT            NO          1     1                   1733961
2 UNUSED              YES        1                      0   0
3 UNUSED              YES        1     0   0
4 UNUSED              YES        1     0                          0
5 UNUSED              YES        1     0   0
6 UNUSED              YES        1     0   0
7 UNUSED              YES        1                      0   0


SQL> select member, a.group#, a.status, b.status, a.archived  from v$log a, v$logfile b where  a.group# = b.group# order by a.group#, member;

MEMBER GROUP# STATUS ARC
--------------------------------------------------------------------------- ---------- ---------------- ------- ------------------ ------- ------------------ -------
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_1_cfxs953z_.log     1 CURRENT NO
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_1_cfxs93y1_.log                       1 CURRENT NO
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_2_cfxs974b_.log       2 UNUSED YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_2_cfxs96bw_.log                       2 UNUSED YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_3_cfxs98t8_.log        3 UNUSED YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_3_cfxs97wp_.log                       3 UNUSED YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_4_cfxs9bvh_.log     4 UNUSED YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_4_cfxs99qc_.log                       4 UNUSED YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_5_cfxs9dx9_.log     5 UNUSED YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_5_cfxs9crd_.log                       5 UNUSED YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_6_cfxs9h4l_.log       6 UNUSED YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_6_cfxs9ftk_.log                       6 UNUSED YES
/data01/app/oracle/fast_recovery_area/ORCL2/onlinelog/o1_mf_7_cfxs9kly_.log       7 UNUSED YES
/data01/app/oracle/oradata/ORCL2/onlinelog/o1_mf_7_cfxs9hyy_.log                      7 UNUSED YES