Oracle Flashback Technologies

Oracle Flashback Technologies - 估算不同时间段闪回日志的产生量

v$flashback_database_stat
监控闪回数据的i/o开销的统计信息，根据之前的系统负载估算闪回空间需求。时间间隔是一小时。

SQL> select * from v$flashback_database_stat  order by begin_time;

BEGIN_TIM END_TIME  FLASHBACK_DATA    DB_DATA  REDO_DATA ESTIMATED_FLASHBACK_SIZE
--------- --------- -------------- ---------- ---------- ------------------------
23-JUN-15 23-JUN-15        5144576   26615808    1989120                268492800
23-JUN-15 23-JUN-15           8192     106496       1536                        0

SQL>

v$flashback_database_stat说明

Column	Datatype	Description
BEGIN_TIME	DATE	Beginning of the time interval
END_TIME	DATE	End of the time interval
FLASHBACK_DATA	NUMBER	Number of bytes of flashback data written during the   interval
DB_DATA	NUMBER	Number of bytes of database data read and written   during the interval
REDO_DATA	NUMBER	Number of bytes of redo data written during the   interval
ESTIMATED_FLASHBACK_SIZE	NUMBER	Value of ESTIMATED_FLASHBACK_SIZE in V$FLASHBACK_DATABASE_LOG at the end of the time interval
CON_ID	NUMBER	The ID of the container to which the data pertains.   Possible values include:   0: This value is used for rows   containing data that pertain to the entire CDB. This value is also used for   rows in non-CDBs.   1: This value is used for rows   containing data that pertain to only the root   n: Where n   is the applicable container ID for the rows containing data