V$FLASHBACK_DATABASE_LOG &&…

最新推荐文章于 2021-04-08 10:52:35 发布

原创最新推荐文章于 2021-04-08 10:52:35 发布 · 871 阅读

0 ·

CC 4.0 BY-SA版权

oracle基础专栏收录该内容

326 篇文章

订阅专栏

本文介绍了Oracle 10g数据库中用于闪回操作的两个重要视图V$FLASHBACK_DATABASE_LOG和V$FLASHBACK_DATABASE_STAT，包括它们的用途、描述以及如何查询这些视图以获取闪回数据库的相关信息。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

V$FLASHBACK_DATABASE_LOG 和 V$FLASHBACK_DATABASE_STAT

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

转自：http://blog.youkuaiyun.com/lwei_998/article/details/6125403

OCP试题

186. You executed the following query in your database:
FROM V$FLASHBACK_DATABASE_LOG;
What would you determine from the output?
A.the time when the last flashback operation in your database was performed
B.the time when the first flashback operation in your database was performed
C.a list of flashback operations performed in your database using SCN and time
D.the approximate time and the lowest system change number (SCN) to which you can flash back your
database
Answer: D

187. These are the details about V$FLASHBACK_DATABASE_STAT:
SQL> DESC V$FLASHBACK_DATABASE_STAT
Name Null? Type
----- -------- ----------
BEGIN_TIME DATE
END_TIME DATE
FLASHBACK_DATA NUMBER
DB_DATA NUMBER
REDO_DATA NUMBER
ESTIMATED_FLASHBACK_SIZE NUMBER
Which two statements regarding the V$FLASHBACK_DATABASE_STAT view are true? (Choose two.)
A.BEGIN_TIME is the time at which Flashback logging is enabled.
B.END_TIME is the time at which the query is executed on the view.
C.REDO_DATA is the number of bytes of redo data written during the interval.
D.This view contains information about flashback data pertaining to the last 24 hours.
E.FLASHBACK_DATA is the amount of flashback data generated since the database was opened.
Answer: CD