ORACLE 12C ORA-00312 Redo fault Handling

First, describe
DB version: 12.1.0.2
System version: 7.0

Second, the processing process
1, error, the database starts on the instance will be abnormally terminated

ORA-00312: online log 3 thread 1: ‘+DATADG/ORCLDG/ONLINELOG/group_3.403.962961193‘ORA-00312: online log 3 thread 1: ‘+DATADG/ORCLDG/ONLINELOG/group_3.405.962961193‘Mon Jan 08 13:35:53 2018USER (ospid: 15155): terminating the instance due to error 16014Mon Jan 08 13:35:53 2018System state dump requested by (instance=1, osid=15155), summary=[abnormal instance termination].System State dumped to trace file /u01/app/oracle/diag/rdbms/orcldg/orcldg/trace/orcldg_diag_15110_20180108133553.trcMon Jan 08 13:35:53 2018Dumping diagnostic data in directory=[cdmp_20180108133553], requested by (instance=1, osid=15155), summary=[abnormal instance termination].Mon Jan 08 13:35:53 2018Instance terminated by USER, pid = 15155Mon Jan 08 13:39:58 2018Starting ORACLE instance (normal) (OS id: 16121)Mon Jan 08 13:39:58 2018CLI notifier numLatches:3 maxDescs:519Mon Jan 08 13:39:58 2018

2. Processing process

 sql> Startup Mount;oracle instance started. Total System Global area 1241513984 bytesfixed size 2923872 bytesvariable size 452985504 byte Sdatabase buffers 771751936 Bytesredo buffers 13852672 bytesdatabase mounted. Sql> sql> Select Group#,sequence#,archived,status from V$log; group# sequence# ARC STATUS---------------------------------------1 356 NO INACTIVE 3 355 No INACTIVE 2 357 no current sql> ALTER DATABASE clear logfile Group 3; ALTER DATABASE clear logfile Group 3*error at line 1:ora-00350:log 3 of Instance Orcldg (thread 1) needs to be Archivedo Ra-00312:online Log 3 thread 1: ' +datadg/orcldg/onlinelog/group_3.403.962961193 ' ora-00312:online log 3 thread 1: ' + datadg/orcldg/onlinelog/group_3.405.962961193 ' sql> sql> ALTER DATABASE clear unarchived logfile Group 3;D atabase Altered. sql> ALTER DATABASE open;database altered.  

3. Description
I'm a ADG here, the main library. This operation leads to Gap, and the standby requires incremental recovery.

ORACLE 12C ORA-00312 Redo fault Handling