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