单项选择题
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.
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.
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？（）
多项选择题 Whatmethodsareavailabletorecoverlostcontrolfiles？（）