--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

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