--关闭数据库，需要将数据库打开到mount状态才能开启闪回功能： SQLgt; shutdown immediate Database closed. Database dismoun
--关闭数据库，需要将数据库打开到mount状态才能开启闪回功能：
sql> shutdown immediate
database closed.
database dismounted.
oracle instance shut down.
sql> show user
user is "sys"
sql> exit
disconnected from oracle database 10g enterprise edition release 10.2.0.1.0 - production
with the partitioning, olap and data mining options
[lubinsu@localhost oracle]$ sqlplus sys/lubinsu as sysdba
sql*plus: release 10.2.0.1.0 - production on sat mar 23 20:14:38 2013
copyright (c) 1982, 2005, oracle. all rights reserved.
connected to an idle instance.
sql> show parameter database
ora-01034: oracle not available
sql> startup nomout
sp2-0714: invalid combination of startup options
sql> startup nomount
oracle instance started.
total system global area 285212672 bytes
fixed size 1218968 bytes
variable size 88082024 bytes
database buffers 188743680 bytes
redo buffers 7168000 bytes
sql> alter database flashback on
2 ;
alter database flashback on
*
error at line 1:
ora-01507: database not mounted
sql> alter database mount
2 ;
database altered.
sql> alter database flashback on
2 ;
alter database flashback on
*
error at line 1:
ora-38706: cannot turn on flashback database logging.
ora-38707: media recovery is not enabled.
--需要开启归档才能使用闪回功能
sql> alter database archivelog on
2 ;
alter database archivelog on
*
error at line 1:
ora-00933: sql command not properly ended
sql> alter database archivelog;
database altered.
sql> alter database flashback on;
database altered.
sql> alter database open;
database altered.
--查看能够闪回的最早的scn号
--如果返回记录为空，，说明没有打开闪回功能
sql> select oldest_flashback_scn from v$flashback_database_log;
oldest_flashback_scn
--------------------
1.3161e+13
sql> select flashback from v$database;
select flashback from v$database
*
error at line 1:
ora-00904: "flashback": invalid identifier
--也可以这么查看是否已经打开闪回功能：
sql> select flashback_on from v$database;
flashback_on
------------------
yes
