V$FLASHBACK_DATABASE_LOG & V$FLASHBACK_DATABASE_STAT

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记录一下ORACE 10g 1Z0-043 中关于闪回的两个视图

SQL> col object_name for a30;
SQL>
SQL> select o.object_name, o.object_type
2 from dba_objects o
3 where o.object_name like 'V$FLASH%';

OBJECT_NAME                                         OBJECT_TYPE
------------------------------                          -------------------
V$FLASHBACK_DATABASE_LOG               SYNONYM
V$FLASHBACK_DATABASE_LOGFILE        SYNONYM
V$FLASHBACK_DATABASE_STAT              SYNONYM
V$FLASHBACK_TXN_GRAPH                     SYNONYM
V$FLASHBACK_TXN_MODS                      SYNONYM
V$FLASH_RECOVERY_AREA_USAGE         SYNONYM

V$FLASHBACK_DATABASE_LOG
显示闪回数据的信息，用来评估当前负载下需要的闪回空间

v$flashback_database_log
Name                                                     Description
------------------------------           --------------------------
OLDEST_FLASHBACK_SCN       Lowest system change number (SCN) in the flashback data, for any incarnation
                                                 闪回数据最小的scn
OLDEST_FLASHBACK_TIME      Time of the lowest SCN in the flashback data, for any incarnation
                                                闪回数据最小的时间
RETENTION_TARGET                Target retention time (in minutes)
                                                闪回保留时间
FLASHBACK_SIZE                   Current size (in bytes) of the flashback data
                                                 闪回数据大小
ESTIMATED_FLASHBACK_SIZE Estimated size of flashback data needed for the current target retention
                                                 评估满足当前闪回保留时间，需要的闪回空间的大小

V$FLASHBACK_DATABASE_STAT
显示数据库收集到的闪回信息
Name                     Description
------------------------ --------
BEGIN_TIME            Beginning of the time interval
                               一段时间间隔的起始时间
END_TIME                End of the time interval
                                一段时间间隔的结束时间
FLASHBACK_DATA    Number of bytes of flashback data written during the interval
                               一段时间内闪回数据的大小(bytes)
DB_DATA                  Number of bytes of database data read and written during the interval
                                 一段时间内数据库读写大小(bytes)
REDO_DATA              Number of bytes of redo data written during the interval
                               一段时间内redo 数据的大小(bytes)
ESTIMATED_FLASHBACK_SIZE Value of ESTIMATED_FLASHBACK_SIZE in V$FLASHBACK_DATABASE_LOG at the

end of the time interval
一段时间间隔的结束时，评估需要闪回空间的大小

参考文档：http://www.oracle.com/global/cn/oramag/oracle/04-may/o34tech_avail.html