To put the database into FORCE LOGGING mode, use the FORCE LOGGING clause in
the CREATE DATABASE statement. If you do not specify this clause, the database is not
placed into FORCE LOGGING mode.

Use the ALTER DATABASE statement to place the database into FORCE LOGGING
mode after database creation. This statement can take a considerable time for
completion, because it waits for all unlogged direct writes to complete.

You can cancel FORCE LOGGING mode using the following SQL statement:

ALTER DATABASE NO FORCE LOGGING;

Independent of specifying FORCE LOGGING for the database, you can selectively
specify FORCE LOGGING or NO FORCE LOGGING at the tablespace level. However, if
FORCE LOGGING mode is in effect for the database, it takes precedence over the
tablespace setting. If it is not in effect for the database, then the individual tablespace
settings are enforced. Oracle recommends that either the entire database is placed into
FORCE LOGGING mode, or individual tablespaces be placed into FORCE LOGGING
mode, but not both.

The FORCE LOGGING mode is a persistent attribute of the database. That is, if the
database is shut down and restarted, it remains in the same logging mode. However, if
you re-create the control file, the database is not restarted in the FORCE LOGGING
mode unless you specify the FORCE LOGGING clause in the CREATE CONTROL FILE
statement

使用FORCE LOGGING子句
1. 数据库创建后 , 将数据库改变为FORCE LOGGING模式时 , 可能需要相当长的时间 ,
因为数据需等待所有不记日志的直接路径写完成
2. ALTER DATABASE NO FORCE LOGGING; 使用该语句来取消FORCE LOGGING模式
3. 可对数据库和表空间级别设置该模式 , 数据库级别优先与表空间级别
4. 数据库关闭后重启 , 依旧为该模式
5. 如果重新创建了控制文件 , 并没有指定FORCE LOGGING子句时 , 数据库重启后该模式
被取消.