首先查看数据库现有模式可使用以下语句

select name,log_mode from v$database

2.关闭数据库

SQL> shutdown immediate

3.启动数据mount状态：

SQL> startup mount;

4、修改数据库为归档模式：

SQL> alter database archivelog;

5、打开数据库，查询：

SQL> alter database open;

SQL> shutdown immediate

Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount ORACLE instance started.

Total System Global Area 1258291200 bytes

Fixed Size 1978336 bytes Variable Size 318771232 bytes Database Buffers 922746880 bytes Redo Buffers 14794752 bytes Database mounted. SQL> alter database archivelog;

Database altered.

SQL> alter database open;

Database altered.