单项选择题
A.uses undo data for roll forward
B.uses Flashback Log for recovery
C.uses online redo logs to roll back
D.uses undo data to roll back the transaction
E.uses Recovery Manager （RMAN） to roll back
F.uses the System Monitor （SMON） background process to perform instance recovery
单项选择题 Initially， for the Automatic Workload Repository （AWR） statistics， the retention period is set to 7 days， the collection interval is set to 30 minutes and the collection level is set to Typical in your production database. You have been using the Memory Advisor for the last three months to generate recommendations for tuning memory components. However， when you observe the Memory Advisor on a Friday， you find that the statistics are available only for two days， Thursday and Friday， of that week. What would have caused the statistics to be removed？（）
单项选择题 You execute the following set of commands to create a database user and to grant the system privileges in your production environment. SQL> CREATE USER user01 IDENTIFIED BY oracle DEFAULT TABLESPACE tbs1 TEMPORARY TABLESPACE temp PROFILE default / SQL> GRANT create session， create table TO user01； While executing the command to create a table， the user gets the following error message and the CREATE TABLE.. command fails. ERROR at line 1： ORA-01950： no privileges on tablespace What could be the possible reason for this error message？（）
单项选择题 Redologfilesarenotmultiplexedinyourdatabase.Redologblocksarecorruptedingroup2，andarchivinghasstopped.Alltheredologsarefilledanddatabaseactivityishalted.Databasewriterhaswritteneverythingtodisk.Whichcommandwouldyouexecutetoproceedfurther？（）