有些测试环境，对数据的准确度要求不是很高的，可以切成非归档模式。
非归档改为归档模式比较简单,设定如下参数就可以了。
然后
startup mount
alter database archivelog;
aler database open
查看archive log lis就可以了
但是归档改为非归档，我试了一下，碰到了以下问题，
---关掉了flashback。。。。。之后重启
SQL>startup mount
SQL> alter database noarchivelog;
Database altered.
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01531: a database already open by the instance
alter database open
*
ERROR at line 1:
ORA-01531: a database already open by the instance
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 242
Next log sequence to archive 244
Current log sequence 244
SQL> show parameter log_archive
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------log_archive_dest string /u01/app/oracle/arch
------------------------------------ ----------- ------------------------------log_archive_dest string /u01/app/oracle/arch
貌似没有改过来，
然后我重启了一次，还是现实归档，尽管提示noarchvelog执行成功，
对于这种情况，我决定重建控制文件。
alter database backup controlfile to trace;
在udump下找到对应的spid的trace文件按
可以用如下的sql来查询
select spid from v$process where addr in (
select addr from v$session where sid in (select sid from v$mystat where rownum
SQL> select spid from v$process where addr='3792379C';
SPID
------------
12718
------------
12718
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
[oracle@oel1 admin]$ cd $ORACLE_BASE
[oracle@oel1 oracle]$ cd admin
[oracle@oel1 admin]$ cd *
[oracle@oel1 PODD]$ cd udump
[oracle@oel1 udump]$ ll *12718*
-rw-r----- 1 oracle dba 10070 Oct 30 22:29 podd_ora_12718.trc
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
[oracle@oel1 admin]$ cd $ORACLE_BASE
[oracle@oel1 oracle]$ cd admin
[oracle@oel1 admin]$ cd *
[oracle@oel1 PODD]$ cd udump
[oracle@oel1 udump]$ ll *12718*
-rw-r----- 1 oracle dba 10070 Oct 30 22:29 podd_ora_12718.trc
CREATE CONTROLFILE REUSE DATABASE "PODD" NORESETLOGS NOARCHIVELOG
把里面的force logging archivelog该为noarchivelog
然后继续
SQL> startup nomount
ORACLE instance started.
ORACLE instance started.
Total System Global Area 398458880 bytes
Fixed Size 1219664 bytes
Variable Size 113247152 bytes
Database Buffers 276824064 bytes
Redo Buffers 7168000 bytes
SQL> CREATE CONTROLFILE REUSE DATABASE "PODD" NORESETLOGS NOARCHIVELOG
。。。。。。
Control file created.
SQL> alter database open;
Database altered.
SQL> archive log list
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 243
Current log sequence 245
这样归档就改为非归档模式了。