Oracle数据库可以运行在2种模式下:归档模式(archivelog)和非归档模式(noarchivelog)
归档模式可以提高Oracle数据库的可恢复性，生产数据库都应该运行在此模式下，归档模式应该和相应的备份策略相结合，只有归档模式没有相应的备份策略只会带来麻烦。
本文简单介绍如何启用和关闭数据库的归档模式。
1.shutdown normal或shutdown immediate关闭数据库
[oracle@jumper oracle]$ sqlplus "/ as sysdba"
SQL*Plus: Release 9.2.0.4.0 - Production on Sat Oct 15 15:48:36 2005
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
2.启动数据库到mount状态
SQL> startup mount;
ORACLE instance started.
Total System Global Area 101782828 bytes
Fixed Size 451884 bytes
Variable Size 37748736 bytes
Database Buffers 62914560 bytes
Redo Buffers 667648 bytes
Database mounted.
3.启用或停止归档模式
如果要启用归档模式，此处使用
alter database archivelog 命令。
SQL> alter database archivelog;
Database altered.
SQL> alter database open;
Database altered.
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /opt/oracle/oradata/conner/archive
Oldest online log sequence 148
Next log sequence to archive 151
Current log sequence 151
如果需要停止归档模式，此处使用：
alter database noarchivelog 命令。
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 101782828 bytes
Fixed Size 451884 bytes
Variable Size 37748736 bytes
Database Buffers 62914560 bytes
Redo Buffers 667648 bytes
Database mounted.
SQL> alter database noarchivelog;
Database altered.
SQL> alter database open;
Database altered.
SQL> archive log list;
Database log mode No Archive Mode
Automatic archival Enabled
Archive destination /opt/oracle/oradata/conner/archive
Oldest online log sequence 149
Current log sequence 152
4.修改相应的初始化参数
Oracle10g之前，你还需要修改初始化参数使数据库处于自动归档模式。
在pfile/spfile中设置如下参数：
log_archive_start = true
重启数据库此参数生效，此时数据库处于自动归档模式。
也可以在数据库启动过程中，手工执行：
archive log start
使数据库启用自动归档，但是重启后数据库仍然处于手工归档模式。
从Oracle10g开始，log_archive_start参数已经废除
