单项选择题
A.The backup status will be marked expired in RMAN recovery catalog.
B.The backup status will be marked deleted in RMAN recovery catalog after you execute the crosscheck command.
C.The backup will be deleted physically from the OS （Operating system）and the backup information is removed from the recovery catalogl
D.The backup status will be marked deleted and you must delete the backup file manually from the OS （Operating system）.
E.The backup status will be marked deleted and you must delete the backup file manually from the OS （Operating system）， if you are not using Oracle Managed Files （OMF）.
多项选择题 YouworkasadatabaseadministratorforSupportcenter.cn.Oneofthedatabaseusersaccidentallydeletedalltherowsofacriticaltableandcommittedthedeleteat1：30p.m.Youseniordatabaseadministrator，SupportCenter，asksyoutoretrievethelostdata.Whichtwoactionswouldyouusetoensurethatthereisnoimpactonotherconnecteduserswhileretrievingthedeletedrows？（）
单项选择题 You work as a database administrator for Supportcenter.cn. When you tried to connect to the database， you received the following error： ERROR： ORA-12541：TNS：no_listener You found that the listener is not running on the server， so you issued the following command in the Listener Control utility to start the listener. lsnrctl>START What statement is true？（）
单项选择题 You execute the following command in your Supportcenter.cn production database to change the width of the CUST_NAME column of the CUSTOMERS table： ALTER TABLE customers MODIFY （cust_nameVARCHAR2 （40）） / When you execute the command， it displays the following error message： ERROR at line 1： ORA-00054： resource busy and acquire with NOWAIT specified What could be the reason for the error message？（）