OS:
Oracle Linux Server release 5.7
DB:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
SQL> startup mount
ORACLE instance started.
Total System Global Area 3340451840 bytes
Fixed Size 2232960 bytes
Variable Size 1912606080 bytes
Database Buffers 1409286144 bytes
Redo Buffers 16326656 bytes
Database mounted.
SQL>
SQL> alter database archivelog;
alter database archivelog
*
ERROR at line 1:
ORA-00265: instance recovery required, cannot set ARCHIVELOG mode
SQL>
SQL> alter database open;
Database altered.
SQL>
SQL> alter system switch logfile;
System altered.
SQL> alter system switch logfile;
System altered.
SQL> alter system switch logfile;
System altered.
SQL>
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL>
SQL> startup mount
ORACLE instance started.
Total System Global Area 3340451840 bytes
Fixed Size 2232960 bytes
Variable Size 1912606080 bytes
Database Buffers 1409286144 bytes
Redo Buffers 16326656 bytes
Database mounted.
SQL>
SQL> alter database archivelog;
Database altered.
SQL>
ORA-00265: instance recovery required, cannot set ARCHIVELOG
原文：http://www.cnblogs.com/hankyoon/p/5174506.html