ORA-01123 cannot start online backup; media recovery not enabled

执行以下语句报错：

SQL> alter tablespace system begin backup;ERROR at line 1:ORA-01123: cannot start online backup; media recovery not enabled

通过查看资料发现时归档未开启，开启归档操作步骤：

SQL> alter database close normal;Database altered.SQL> select open_mode from v$database;OPEN_MODE------------------------------------------------------------MOUNTEDSQL> alter database archivelog;Database altered.

发现这时候要重启数据库，否则无法直接切换到读写模式：

SQL> alter database open;alter database open*ERROR at line 1:ORA-16196: database has been previously opened and closedSQL> shutdown immediate;ORA-01109: database not openDatabase dismounted.ORACLE instance shut down.SQL> startup;ORACLE instance started.Total System Global Area 6680915968 bytesFixed Size                  2213936 bytesVariable Size            3556771792 bytesDatabase Buffers         3087007744 bytesRedo Buffers               34922496 bytesDatabase mounted.Database opened.