1、Which two are true about reclaiming space used by Flashback logs in Oracle Database 19c and later releases?
A)Space is only reclaimed when there is space pressure in the Fast Recovery Area(FRA)
B)Space is always reclaimed automatically when the retention period for Flashback logs is lowered
C)Space might be reclaimed proactively before space pressure occurs
D)Space is always reclaimed proactively before space pressure occurs
E) Space might be reclaimed automatically when the retention period for Flashback logs is lowered
答案: CE
RMAN uses flashback logs to undo changes to a point before the target time or SCN, and then uses archived redo logs to recover the database forward to make it consistent这是先回滚再前滚的过程。
If the flash recovery area is full, then an archived redo log may be automatically deleted by the flash recovery area to make space for other files. In such a case, any flashback logs that would require the use of that redo log file for the use of FLASHBACK DATABASE are also deleted.删除archivelog后对应的flashback logs也没有用了，会被自动删除，因此a不对，c对。
DB_FLASHBACK_RETENTION_TARGET specifies the upper limit (in minutes) on how far back in time the database may be flashed back. 这个参数不是强制的。
https://docs.oracle.com/cd/B19306_01/backup.102/b14192/rpfbdb003.htm#BABCAGIB
2、Which two are true about server-generated alerts?
A)Stateless alerts can be cleared manually
B)Stateless alerts are automatically cleared after one day.
C)Stateful alerts are purged automatically from the alert history after one day
D)Stateless alerts can be purged manually from the alert history.
E) Stateful alerts must be cleared by a DBA to resolve the problem identified in the alert.
答案: AD
E中状态消失后就被清理，状态可以自动消除，无需dba干预
使用命令emcli clear_stateless_alerts可以手工清除stateless alerts。
Stateful alerts是指超过阈值的报警状态，低于阈值后被清理，从来视图DBA_OUTSTANDING_ALERTS被迁移到DBA_ALERT_HISTORY。
Stateless alerts像是一个时间点的报警，说明系统曾经发生过什么错误，例如ora-的错误。这类报警直接保存到DBA_ALERT_HISTORY中，不会自动清理，只能收到清理。
注意purge和clear的区别。
3、Which three are true about upgrading Oracle Grid Infrastructure?
A)The newer version is installed in a separate Oracle Grid Infrastructure home on the same server as the existing version
B)A direct upgrade can be performed only from the immediately preceding Oracle Grid Infrastructure version
C)The upgrade process will automatically install all mandatory patches for the current version of Oracle Grid Infrastructure
D)Only the grid user can perform the upgrade
E)Existing Oracle Database instances must be shut down before starting the upgrade
F）An existing Oracle base can be used.
答案: AEF
A 对的，是out-of-place upgrades,
B 不对，参见： https://docs.oracle.com/en/database/oracle/oracle-database/19/cwlin/options-for-oracle-grid-infrastructure-upgrades-and-downgrades.html#GUID-B3BED6A8-1718-4795-A5EB-84ABC2A15CF6 期中from the immediately preceding 表示“从最近的前面”
D不对：The same user that owned the earlier release Oracle Grid Infrastructure software must perform the Oracle Grid Infrastructure 19c upgrade.
4、Which two are true about the Program Global Area(PGA)and its management in an Oracle database instance?
A)PGA_AGGREGATE_LIMIT is a hard limit on the PGA size for any one session
B)The entire PGA is located in the System Global Area(SGA)when using shared servers
C)The private SQL area(UGA)is located in the System Global Area(SGA)when using shared servers
D)Sorts and Hash Joins use PGA memory.
E) The private SQL area(UGA)is located in the System Global Area(SGA)when using dedicated servers
答案: CD
PGA_AGGREGATE_TARGET 设置起到的是目标的作用，而非限制。
5、You plan to perform cross-platform PDB transport using XTTS. Which two are true?
A)A backup of the PDB must exist, taken using the BACKUP command with the TO PLATFORM clause
B) The source PDB can be in MOUNT or OPEN state
C)The source PDB must be in MOUNT state.
D)The source PDB must not be an application root.
E)Automatic conversion of endianess occurs.
F)The source and target platforms must have the same endianess
答案: BF
传输表空间也不能传输SYSTEM表空间或者SYS用户拥有的对象
Cross-platform transportable database can only be performed between platforms that have the same endian format.因此E不对，F对，底层的原理是system表空间不能进行endian转换
A不对，备份可以用TO PLATFORM也可以用FOR TRANSPORT。很多培训机构都选A。
B对，C不对，根据官方文档，pdb也可以用Inconsistent Backups。
6、Which two are true about the automatic execution of operating system scripts when performing silent mode installation starting from Oracle Database 19c?
A) The installer will prompt for the root or sudo password
B) Silent install always runs operating scripts automatically.
C) The response file can specify the root or sudo password
D)The response file must contain the root or sudo password
E) The response file can specify the path of the sudo program
答案: AE
https://docs.oracle.com/en/database/oracle/oracle-database/19/ladbi/how-response-files-work.html
B execute the root script manually.
C D都不对，response file中没有密码的选项，可能是为了安全。
