The UNDO_RETENTION parameter in your database is set to 1000 and undo retention is not guaranteed. Which statement regarding retention of undo data is correct？（）A、Undo data becomes obsolete after 1，000 seconds.B、Undo data gets refreshed after every 1，000 seconds.C、Undo data will be stored permanently after 1，000 seconds.D、Committed undo data would be retained for 1，000 seconds if free undo space is available.E、Undo data will be retained in the UNDO tablespace for 1，000 seconds，then it gets moved to the TEMPORARY tablespace to provide read consistency.
The UNDO_RETENTION parameter in your database is set to 1000 and undo retention is not guaranteed. Which statement regarding retention of undo data is correct？（）
- A、Undo data becomes obsolete after 1，000 seconds.
- B、Undo data gets refreshed after every 1，000 seconds.
- C、Undo data will be stored permanently after 1，000 seconds.
- D、Committed undo data would be retained for 1，000 seconds if free undo space is available.
- E、Undo data will be retained in the UNDO tablespace for 1，000 seconds，then it gets moved to the TEMPORARY tablespace to provide read consistency.
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对任意两个事件A与B，有( )。A．P(AB)=P(A)+P(B)-P(A∪B)B．P(AB)=P(A)P(B)C．P(A-B)=P(A)-P(AB)D．P(A)P(B｜A)=P(B)P(A｜B)E．P(A∪B)=P(A)+P(B)
设A、B、C为随机事件，则( )。A.P(A-B-C)=P(A)-P(AB)-P(AC)-P(BC)+P(ABC)B.P(A-B-C)=P(A)-P(AB)-P(AC)+P(ABC)C.P(A-B-C)=P(A)-P(AB)-P(BC)+P(ABC)D.P(A-B-C)=P(A)-P(AC)-P(BC)+P(ABC)
对于概率P（A∪B）的意思是（ ）。A.P（A∪B）=P（A）+P（B）-P（A∩B）B.P（A∪B）=P（A）+P（B）-P（AB）C.P（A∪B）=P（A）+P（B）+P（A∩B）D.P（A∪B）=P（A）+P（B）+P（AB）
对于概率P（A∪B）的意思是（ ）。A：P（A∪B）=P（A）+P（B）-P（A∩B）B：P（A∪B）=P（A）+P（B）-P（AB）C：P（A∪B）=P（A）+P（B）+P（A∩B）D：P（A∪B）=P（A）+P（B）+P（AB）
前趋图是一个有向无环图，记为：→=(P i ，P j )|P i 完成时间先于 P j 开始时间}。假设系统中进程 P=(P 1 ，P2， P3， P 4 ， P 5 ，P 6 ， P 7 ，P 8 }且进程的前趋图如下：那么，该前驱图可记为（）。A.→={(P1,P2),(P1,P3),(P1,P4 ),(P2,P5),（P3,P2）,（P3,P4）,（P3,P6）,（P4,P7）,（P5,P8）,（P5,P6）,（P7,P8）}B.→={(P1,P2),(P1,P3),(P1,P4),(P2,P5),（P3,P2）,（P3,P4）,（P3,P6）,（P4,P7）,（P5,P8）,（P6,P8）,（P7,P8）}C.→={(P1,P2),(P1,P3),(P1,P4),(P2,P5),（P3,P2）,（P3,P4）,（P3,P5）,（P4,P6）,（P4,P7）,（P6,P8）,（P7,P8）}D.→={(P1,P2),(P1,P3),(P1,P4),(P2,P5),（P3,P2）,（P3,P4）,（P3,P5）,（P4,P6）,（P4,P7）,（P7,P8）,（P6,P8）}
前趋图是一个有效无环图,记为→={pi,pj，pi完成时间先于pj开始时间}。假设系统中进P={p1,p2,p3,p4,p5,p6,p7,p8}，且进程的前趋图如下。那么该前驱图可记为（请作答此空）图中（ ）A.→={(P1,P2),(P1,P3),(P1,P4),(P2,P5),(P3,P2),(P3,P4),(P3,P6),(P4,P7),(P5,P8)B.→={(P1,P2),(P1,P4),(P2,P3),(P2,P5),(P3,P4),(P3,P6),(P4,P7),(P5,P6),(P6,P8),(p7,p6)}C.→={(P1,P2),(P1,P4),(P2,P5),(P3,P2),(P3,P4),(P3,P6),(P4,P6),(P4,P7),(P6,P8),(p7,p8)}D.→={(P1,P2),(P1,P3),(P2,P4),(P2,P5),(P3,P2),(P3,P4),(P3,P5),(P4,P7),(P6,P8),(p7,p8)}
前趋图(Precedence Graph) 是一个有向无环图，记为：→={（Pi，Pj ）|Pi must complete before Pj may strat}。假设系统中进程P={P1，P2，P3，P4，P5，P6，P7，P8}，且进程的前驱图如下：那么前驱图可记为：( )A. →={(P2,P1),(P3,P1),(P4,P1),(P6,P4),(P7,P5）,（P7,P6）,（P8,P7）}B. →={（P1,P2）,(P1,P3),(P1,P4),(P2,P5),(P5,P7),(P6,P7）,（P7,P8）}C. →={（P1,P2),(P1,P3),(P1,P4),(P2,P5),（P3,P5),(P4,P6),(P5,P7),(P6,P7),(P7,P8)}D. →={(P2, P1), (P3,P1),(P4,P1),(P5,P2),(P5,P2),(P5,P3),(P6,P4),(P7,P5), (P7,P6),(P8,P7)}
用气相色谱法测定食品中的有机氯农药DDT，不同异构体的出峰顺序依次是（ ）A、p，p’-DDE、o，p’-DDT、p，p’-DDD、p，p’-DDTB、o，p’-DDT、p，p’-DDD、p，p’-DDT、p，p’-DDEC、p，p’-DDD、p，p’-DDT、p，p’-DDE、o，p’-DDTD、p，p’-DDT、p，p’-DDE、o，p’-DDT、p，p’-DDDE、p，p’-DDE、p，p’-DDD、p，p’-DDT、o，p’-DDT
You are working on a test database where instance recovery takes a considerable amount of time.How can reduce the recovery time？（）A、By multiplexing the control filesB、By multiplexing the redo log filesC、By decreasing the size of redo log filesD、By configuring mean time to recover （MTTR） to a lower valueE、By setting the UNDO_RETENTION parameter to a higher value
多选题You work as a database administrator for Certkiller .com. You want to create your database with the automatic undo management feature enable.Which two tasks must you perform to achieve this？（）ASet the UNDO_RETENTION parameter to AUTO.BCreate an initial undo segment in undotablespace.CSet the UNDO_RETENTION parameter to 900 or moreDSet the initialization parameter UNDO_MANAGEMENT to AUTOESet the UNDO_MANAGEMENT parameter to the name of an undotablespace
多选题Which three pieces of information are considered while deciding the size of the undo tablespace in your database？（）Athe size of an undo blockBthe size of the redo log filesCundo blocks generated per secondDthe size of the database buffer cacheEthe value of the UNDO_RETENTION parameter
多选题You are working on a test database where instance recovery takes a considerable amount of time. How can reduce the recovery time？（）ABy multiplexing the control filesBBy multiplexing the redo log filesCBy decreasing the size of redo log filesDBy configuring mean time to recover （MTTR） to a lower valueEBy setting the UNDO_RETENTION parameter to a higher value
单选题Which statement is true about the UNDO_RETENTION parameter when retention guarantee is notenabled（）AIt is the time period after which the undo data becomes obsolete.BIt is the time period after which the committed undo data would be transferred to a temporarytablespace.CIt is the minimum time period up to which the committed undo data would be retained if free undo spaceis available.DIt is the time period after which the undo data is transferred to the Flash Recovery Area to provide readconsistency.
单选题You work as a database administrator for Supportcenter.cn. Your database is configured for automatic undo management. UNDO_RETENTION is set to 3 hours. You want to flash back a table that was created last year. How far back can the flashback query go？（）A3 hoursB6 monthsCuntil last yearDuntil last commitEuntil the point when the undotablespacewas refreshedFuntil the database is shut down and the memory erased
单选题In which situation may the UNDO_RETENTION parameter be ignored， even if it is set to a value（）Awhen the data file of the undo tablespace is autoextensibleBwhen there are more than one undo tablespaces available in the databaseCwhen the undo tablespace is of a fixed size and retention guarantee is not enabledDwhen the undo tablespace is autoextensible and retention guarantee is not enabled
单选题In which situation is the UNDO_RETENTION parameter be ignored， even if it is set to a value（）AWhen the data file of the undo tablespace is autoextensibleBWhen there are more than one undo tablespaces available in the databaseCWhen the undo tablespace is of a fixed size and retention guarantee is not enabledDWhen the undo tablespace is autoextensible and retention guarantee is not enabled
单选题On Friday at 11:30 am you decided to flash back the database because of a user error that occurred at 8:30am. Which option must you use to check whether a flashback operation can recover the database to the specified time?（）ACheck the alert log fileBQuery the V$FLASHBACK_DATABASE_LOG viewCQuery the V$RECOVERY_FILE_DEST_SIZE viewDQuery the V$FLASHBACK_DATABASE_STAT viewECheck the value assigned for the UNDO_RETENTION parameter
单选题用气相色谱法测定食品中的有机氯农药DDT，不同异构体的出峰顺序依次是（ ）Ap，p’-DDE、o，p’-DDT、p，p’-DDD、p，p’-DDTBo，p’-DDT、p，p’-DDD、p，p’-DDT、p，p’-DDECp，p’-DDD、p，p’-DDT、p，p’-DDE、o，p’-DDTDp，p’-DDT、p，p’-DDE、o，p’-DDT、p，p’-DDDEp，p’-DDE、p，p’-DDD、p，p’-DDT、o，p’-DDT