OCP-1Z0-053-V12.02-667题

667.What does the DB_FLASHBACK_RETENTION_TARGET parameter configure?

A. An upper limit on how far you can flash back the database, depending on the information in the redo

logs

B. An upper limit on how far you can flash back the database, depending on the information in the undo

tablespace

C. The amount of time for which the flashback data is to be kept in the flash recovery area, provided that

there is enough space

D. The amount of time for which the flashback data is guaranteed to be kept in the undo tablespace,

provided that there is enough space

Answer: C

答案解析

默认值 1440分钟

改变：ALTER SYSTEM ... SID='*'

ys@TEST0910> show parameter DB_FLASHBACK_RETENTION_TARGET

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_flashback_retention_target integer 1440


sys@TEST0910> alter system set DB_FLASHBACK_RETENTION_TARGET=1500;

System altered.

sys@TEST0910> show parameter DB_FLASHBACK_RETENTION_TARGET

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_flashback_retention_target integer 1500

DB_FLASHBACK_RETENTION_TARGET

specifies the upper limit (in minutes) on how far back in time the database may be flashed back. How far back one can flashback a database
depends on how much flashback data Oracle has kept in the fast recovery area.

官方参考：http://docs.oracle.com/cd/E11882_01/server.112/e40402/initparams061.htm#sthref198