Oracle 11gr1 flash back to flashback

Open Database flashback
1. Check whether flashback is enabled for a database. There are two simple methods:
(1) directly query the database
SQL> select name, log_mode, flashback_on from v $ database;

NAME LOG_MODE FLASHBACK_ON
---------------------------------------
ORA11G ARCHIVELOGNO--> Flashback is not enabled

(2) view background processes
Oracle @ BMP 1A: ~>Ps-ef | grep rvw | grep-v grep
Oracle 9288 1 0? 00:00:00 ora_rvwr_ora11g --> flashback has opened www.bkjia.com

2. If flashback is not enabled for the database, open flashback:
(1) determine the storage path of flashback
SQL> show parameter recovery

NAME TYPE VALUE
----------------------------------------------------------------------
Db_recovery_file_dest string
Db_recovery_file_dest_size big integer 0
Recovery_parallelism integer 0
Modify db_recovery_file_dest:
SQL> alter system set db_recovery_file_dest = '/home/oracle/flashback' scope = both;
Alter system set db_recovery_file_dest = '/home/oracle/flashback' scope = both
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified the value is invalid
ORA-19802: cannot use DB_RECOVERY_FILE_DEST without DB_RECOVERY_FILE_DEST_SIZE
The error above is becauseBefore setting db_recovery_file_dest, you must set db_recovery_file_dest_size., So:
SQL> Alter system set db_recovery_file_dest_size = 20G scope = both;

System altered.

SQL> show parameter recovery

NAME TYPE VALUE
------------------------------------------------------------------------
Db_recovery_file_dest string
Db_recovery_file_dest_size big integer 20G
Recovery_parallelism integer 0
SQL>Alter system set db_recovery_file_dest = '/home/oracle/flashback' scope = both;

System altered.

SQL> show parameter recovery

NAME TYPE VALUE
------------------------------------------------------------------------
Db_recovery_file_dest string/home/oracle/flashback
Db_recovery_file_dest_size big integer 20G
Recovery_parallelism integer 0

(2) Open flashback
SQL> alter database flashback on;
Alter database flashback on
*
ERROR at line 1:
ORA-38759: Database must be mounted by only one instance and not open.
The error above is becauseThe flashback to open the database must be in the mount status., So:
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.

Total System Global Area 5344731136 bytes
Fixed Size 2169104 bytes
Variable Size 2130708208 bytes
Database Buffers 3204448256 bytes
Redo Buffers 7405568 bytes
Database mounted.
SQL>Alter database flashback on;

Database altered.

SQL> alter database open;

Database altered.

SQL> select name, log_mode, flashback_on from v $ database;

NAME LOG_MODE FLASHBACK_ON
---------------------------------------
ORA11G ARCHIVELOGYES