闪回数据库

• 1. Configure the following parameters in parameter file(init.ora) or spfile

• Example:

  \**db_recovery_file_dest参数为0时，不能设定flash_recovery_area参数*\
   SQL> alter system set db_recovery_file_dest_size=2147483648 scope=spfile;
   SQL> alter system set db_recovery_file_dest=‘/u01/app/oracle/flash_recovery_area‘ scope=spfile;
   SQL> alter system set DB_FLASHBACK_RETENTION_TARGET=2880; (2 days) |

• 2. Turn flashback on:

    SQL> Startup mount exclusive;
    SQL> alter database archivelog;
    SQL> Alter database flashback on;
    SQL> Alter database open; |

• 3. Check status

  SQL> SELECT flashback_on, log_mode FROM gv$database;
      SQL> SELECT estimated_flashback_size FROM gv$flashback_database_log;
  $ ps -eaf | grep rvwr |

禁用Flashback Database

Alter database flashback on;

Flashback Database Using SQL or RMAN Commands

1.使用SQLPLUS

• Use an SCN or a time stamp in the SQL version
• Example: Flash back the database to a day before using SQL

  SQL> shutdown immediate;
  SQL> startup mount exclusive;
  SQL> flashback database to timestamp(sysdate-1);
  SQL> alter database open resetlogs;

2.使用 RMAN

• Using RMAN, you can flash back to a time stamp, SCN, or log sequence number (SEQUENCE) and thread number (THREAD).
• Example:

    RMAN> FLASHBACK DATABASE TO TIME = TO_DATE(‘2002-12-10 16:00:00‘,‘YYYY-MM-DD HH24:MI:SS‘);
    RMAN> FLASHBACK DATABASE TO SCN=23565;
    RMAN> FLASHBACK DATABASE TO SEQUENCE=223 THREAD=1;

视图

• **VFLASHBACKDATABASELOG???monitortheestimatedandactualsizeoftheflashbacklogsintheflashrecovery?Checkflashrecoveryareadiskquota:‘‘‘SQL>selectretentiontarget,flashbacksize,estimatedflashbacksizeFROMVFLASHBACK_DATABASE_LOG;

  - Determine the current flashback window:

  SQL> SELECT oldest_flashback_scn,oldest_flashback_time FROM VFLASHBACKDATABASELOG;‘‘‘???VFLASHBACK_DATABASE_STAT -** monitors the overhead of logging flashback data in the flashback logs. It contains at most 24 rows, with one row for each of the last 24 hours.
  • The flashback generation for the last hour:

    SQL> select to_char(end_time,‘yyyy-mm-dd hh:miAM‘) end_timestamp, flashback_data, db_data, redo_data from v$flashback_database_stat where rownum=1;

从Flashback Database中排除表空间

SQL> ALTER TABLESPACE <ts_name> FLASHBACK {ON|OFF}
SQL> SELECT name, flashback_on 2 FROM v$tablespace;

Note

• Take the tablespace offline before you perform the database flashback operation.
• After performing Flashback Database, drop the tablespace or recover the offline files with traditional point-in-time recovery.

Flash back a RESETLOGS operation

可以闪回到resetlogs之前的一个时间点

SQL> FLASHBACK DATABASE TO BEFORE RESETLOGS;

Limitations

• You cannot use Flashback Database in the following situations:

• The control file has been restored or re-created.

• A tablespace has been dropped.
• A data file has been shrunk
• 需要开启FRA特性

闪回数据库的一些命令:

\**闪回到指定的日期**\
FLASHBACK DATABASE TO TIMESTAMP(to_data(‘2015.07.11 20:03:00‘,‘YYYY.MM.DD HH24:MI:SS‘));
\**闪回到5分钟之前**\
FLASHBACK DATABASE TO TIMESTAMP SYSDATE-(1/24/12);
FLASHBACK DATABASE TO BEFORE TIMESTAMP my_date;
\**回退到过去的某个SCN点**\
FLASHBACK DATABASE TO SCN my_scn;
FLASHBACK DATABASE TO BEFORE SCN my_scn;
\**回退到某个Log Sequence号*\
flashback database to sequence=223 thread=1;
\**回退完成之后以resetlogs的方式打开数据库*\
alter database open resetlogs;

\**也可以创建一个恢复点*\
CREATE RESTORE POINT before_changes;
FLASHBACK DATABASE TO RESTORE POINT before_changes;