[bbk4345]小布-OCP 042全真试题讲解

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[bbk4345]小布-OCP 042全真试题讲解

在非归档模式下，你只能做冷备；做热备是无法保证数据的一致性的.

在归档模式下，是可以做热备的，其原理是根据归档日志文件来实现数据的一致性.

• 1、Your test database is running in NOARCHIVELOG mode.What are the implications of this?
  • You can perform open database backups.
  • You can perform closed database backups.
  • You cannot perform schemal-level logical backups.
  • You can perform the backup of only the SYSTEM tablespace when the databse is open.
• 2、Which two statements about Recovery Manager(RMAN) backups are true?(Choose two)
  • A.Online redo log files can be backed up.
  • B.Archived redo log files are backed up.
  • C.Only used data blocks can be backed up as backup sets.
  • D.Only consistent database backups can be performed.
  • E.RMAN backup can be taken if the database is configureed in ARCHIVELOG mode.

在非归档模式下，RMAN是可以备份数据库的，不过必须把数据库设置成为mount状态.

使用RMAN备份数据库，只备份Data Files 和 Archive log  file.

• 3、The database is open,and you plan to perform Recovery Manager(RMAN)backups.Which three statements are true about these backups?(Choose trhee)
  • A.The backups would be consistent.
  • B.The backups would be inconsistent.
  • C.The backups need to be restored and database has to be recovered in case of a media failure. 
  • D.The backups need not be restored during recovery in case of a media failure.
  • E.The backups would be possible only if the database is running in ARCHIVELOG mode.
  • F.The backups would be possible only if the database is running in NOARCHIVELOG mode.

restore就是拷贝备份集，recovery就是利用归档日志文件更新备份集，是备份集达到你任何想要的状态.

恢复的时候，肯定是先restore，然后再recovery.

在数据库打开的状态下，使用RMAN进行备份，数据库必须处于归档模式下.

• 4、You perform differential incremental level 1 backups of your database on each working day and level 0 backup on Sundays.
  • Which two statements are true about the differential incremental backups?(choose two) 
  • A.The backup performed on Sundays contains all the blocks that have ever been use in the database.
  • B.The backup performed on Sundays contains all the blocks that have changed since the last level 1 backup.
  • C.The backup performed on each working day contains all the blocks that have changed since the last level 0 or level 1 backup.
  • D.The backup performed on each working day contains all the blokcs that have changed since the last level 0 backup.

level 0相当于一种特殊的增量备份.

level 0就相当于全备,但是0级备份不等于全备.其中全备不能作为增量备份的基础，而0级备份则可以作为增量备份的基础.

0级备份的定义（全备），就是:The backup performed on Sundays contains all the blocks that have ever been use in the database. 

• 5、According to your backup strategy,you performed an incremental level 0 backup of your database.Which statement regarding this backup is true?
  • A.The backup is similar to image copy.
  • B.The backup contains all used data blocks.
  • C.The backup contains only unused data blocks.
  • D.The backup contains all data blocks changed since the last incremental level 1 backup.

image copy类似于cp,dd命令的备份，而level 0的备份属于备份集的备份，有着本质的区别.

• 6、On which three can you use Recovery Manager(RMAN) to perform incremental backup ?(Choose three)
  • A.data files
  • B.control files
  • C.tablespaces
  • D.password files
  • E.parameter file
  • F.whole database
  • G.flashback log file
  • H.archived log file
  • I.change tracking file

增量备份主要是针对于数据文件块的备份，只把那些变化的块备份下来.  

控制文件是不分块的，RMAN备份只是镜像的拷贝.

flashback log file、archive log file、change tracking file是对整个数据库文件的拷贝，不分块的概念的.因此不能进行增量备份.

• 7、You backed up the control file to trace.Which statement is true about the trace file generated?
  • A.The trace file is in binary format.
  • B.The trace file has a SQL script to re-create the control file.
  • C.The trace file is a backup set created during the backup of the control file.
  • D.The trace file contains the instructions to manually re-create the control file.
  • E.The trace file is an image copy of the control file created during the backup of the control file.

trace file一般就是日志文件，日志文件一般就是文本文件.

trace file没有备份集的概念的，备份集的概念是针对于数据文件的.

所谓的image copy就是二进制文件.

• 8、Your database is in NOARCHIVELOG mode,after which two operations you should take the backup of control file?(Choose two)
  • A.adding a new user to the database
  • B.dropping a user from the database
  • C.dropping a table from the database
  • D.dropping a data file from a tablespace
  • E.adding a new tablespace to the database.

什么时候需要备份控制文件，肯定是当控制文件的内容发生变化了，才会进行备份.

控制文件主要记录了数据库的结构化的信息.

• 9、You executed the following command to back up your control file:

ALTER DATABASE BACKUP CONTROLFILE TO TRACE;

Which initialization parameter is used to specify the location of the trace file?

• • A.USER_DUMP_DEST
  • B.CORE_DUMP_DEST
  • C.TRACE_DUMP_DEST
  • D.BACKUP_DUMP_DEST
  • E.BACKGROUND_DUMP_DEST

Your database is configured in NOARCHIVELOG mdoe.All the control files have been lost due to a hard disk failure bu the data files are not lost.You have the closed whole database backup available to you.

那么这种情况下，你能否重构数据文件呢?答案不能.因为数据库时处于非归档模式下.

• 10、Your database is configured in NOARCHIVELOG mode.All the control files have been lost due to a hard disk failure but the data files are not lost.You have closed whole database backup availbale to you.

Which two statements are true in this scenario?(Choose two)

• • A.the instance aborts.
  • B.The database cannot be recovered.
  • C.The database can be recovered by restoring the control files from the backup.(时间点不一致，无法通过拷贝方式，直接使用控制文件)
  • D.The database remains opened and you have to shut it down with the ABORT option.
  • E.The database can be restored till the point of the last closed whole database backup.
• 11、In your database,the Log Writer(LGWR)process is unable to write to a member of a current redo log group due to read/write failure.Which two effects would you see in your database?(Choose two)
  • A.the database instance aborts.
  • B.the database operation temporaily halts till the member becomes available.
  • C.Writing proceeds as normal.LGWR writes to the available members of a group and ignores the unavailable members.
  • D.The member would be marked as STALE and an error message would be written to the alert log file and LGWR trace file.
  • E.The status of the group changes to INACTIVE and an error message would be written to the alert log file and LGWR trace file.

log file group的状态，CURRENT、INACTIVE、STALE

当前正在使用的日志组的状态为:CURRENT

即将或者正在进行归档的日志文件为:INACTIVE

脏了的日志文件为STALE.