现象：
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-16038: log 3 sequence# 857 cannot be archived
ORA-12154: TNS:could not resolve the connect identifier specified
ORA-00312: online log 3 thread 1: '/u01/app/oracle/oradata/oralin/redo03.log'
解决方案：
1，查一下你是否在DG中；
2，查log_archive_dest_n 除1外，是否还有设置，如果有设置，查log_archive_dest_state_n除1外是否还有enable，如果有enable，则改为defer；（作此原因，要确定是否以前做过DG的实验，且为测试数据库，否则轻易不要修改）
3，以上配置都正确，则清空所有的log group：
SQL> alter database clear unarchived logfile group 1;
Database altered.
SQL> alter database clear logfile group 1;
Database altered.
SQL> alter database clear unarchived logfile group 2;
Database altered.
SQL> alter database clear logfile group 2;
Database altered.
SQL> alter database clear unarchived logfile group 3;
Database altered.
SQL> alter database clear logfile group 3;
Database altered.
SQL> alter database open;
Database altered.
4，如果open后再次切日志，还会出现此问题，则直接recover。
SQL> alter system archive log current;
alter system archive log current
*
ERROR at line 1:
ORA-16038: log 1 sequence# 860 cannot be archived
ORA-12154: TNS:could not resolve the connect identifier specified
ORA-00312: online log 1 thread 1: '/u01/app/oracle/oradata/oralin/redo01.log'
SQL> recover database until cancel;
