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单项选择题

What does the SCN represent？（）  

A. The system change number， which is a point in time relative to transactions within a given database.
B. A number that represents time. Thus， at 1300 hours， the SCN is the same on all databases. 
C. The security change number， which represents the security code that is needed to access any database structure.
D. A conversion factor that converts internal database time to external clock time.
E. UTC time in the database，providing a standardized way of tracking time in Oracle.

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热门试题

单项选择题You have lost all your online redo logs. As a result， your database has crashed. You have tried to restart the database and clear the online redo log files， but when you try to open the database you get the following error.   SQL> startup ORACLE instance started.  Total System Global Area 167395328 bytes Fixed Size 1298612 bytes Variable Size 142610252 bytes Database Buffers 20971520 bytes Redo Buffers 2514944 bytes Database mounted.  ORA-00313： open failed for members of log group 2 of thread 1 ORA-00312： online log 2 thread 1： ，， oracle01 oradata orcl redo02a.log ORA-27037： unable to obtain file status Linux Error： 2： No such file or directory Additional information： 3  ORA-00312： online log 2 thread 1： ，， oracle01 oradata orcl redo02.log ORA-27037： unable to obtain file status Linux Error： 2： No such file or directory Additional information： 3  SQL> alter database clear logfile group 2； alter database clear logfile group 2 * ERROR at line 1：  ORA-01624： log 2 needed for crash recovery of instance orcl （thread 1） ORA-00312： online log 2 thread 1： ，， oracle01 oradata orcl redo02.log ORA-00312： online log 2 thread 1： ，， oracle01 oradata orcl redo02a.log   What steps must you take to resolve the error？（） a. Issue the recover database redo logs command.  b. Issue the Startup Mount command to mount the database.  c. Restore the last full database backup.  d. Perform a point-in-time recovery， applying all archived redo logs that are available.  e. Restore all archived redo logs generated during and after the last full database backup.  f. Open the database using the alter database open resetlogs command.  g. Issue the alter database open command.

A.b， a， f
B.e， b， a， f
C.e， b， a， g
D.b， a， g
E.c， e， b， d， f

单项选择题Your ARCHIVELOG-mode database has lost three datafiles and shut down. One is assigned to the SYSTEM tablespace and two are assigned to the USERS tablespace. You can choose from the following steps to recover your database：   a. Restore the three database datafiles that were lost.  b. Issue the Startup Mount command to mount the database.  c. Issue the alter database open command.  d. Issue the alter database open resetlogs command.  e. Recover the database using the recover database command. f. Recover the datafiles with the recover datafile command.  g. Take the datafiles offline.  Which is the correct order of these steps in this case？（）

A.a， b， e， c
B.b， e， d
C.a， b， d， c
D.b， g， c， f
E.a， b， d， f

多项选择题Whatmethodsareavailabletorecoverlostcontrolfiles？（）

A. Backup control file.
B. Emergency control file.
C. The create controlfile command.
D. The restore controlfile SQL*Plus command.
E. No backup is required. The database will re-create the control file when it is discovered to be lost.

单项选择题Yourdevelopershaveaskedyoutorestorethedevelopmentdatabase，whichisinNOARCHIVELOGmode，backtolastTuesdaythe20th.YourlastbackupisfromMondaythe19th.Whatdoyoudo？（）

A. Restore the 19ths backup， restore all archived redo logs， recover the database to the 20th，and open the database.
B. Tell them that their request cannot be met with the current backup strategy.
C. Restore the 19ths backup， apply the online redo logs，and open the database.
D. Switch the database into ARCHIVELOG mode，restore the 19th’s backup，restore all archived redo  logs，and recover the database to the 20th.
E. Use the recover database command to roll back the database from today to the 19th of the month.

单项选择题You have lost all your database control files. To recover them， you are going to use the results of the alter database backup controlfile to trace command. Your datafiles and your online redo logs are all intact.  Which of the following is true regarding your recovery？（）

A. You will need to open the database with the resetlogs command.
B. All you need to do is execute the trace file from SQL*Plus and it will perform the recovery for you.
C. You will use the resetlogs version of the create controlfile command.
D. You will use the noresetlogs version of the create controlfile command.
E. You will use the trace file to create a backup control file， and then you will recover the database with the recover database using backup controlfile command