单项选择题

YouworkasadatabaseadministratorforCertkiller.com.TheUNDO_RETENTIONparameterinyourdatabaseissetto1000andundoretentionisnotguaranteed.Whichstatementregardingretentionofundodataiscorrect？（）

A.Undodatabecomesobsoleteafter1，000seconds.
B.Undodatagetsrefreshedafter1，000seconds.
C.Undodatawillbestoredpermanentlyafter1，000seconds.
D.Committedundodatawouldberetainedfor1，000secondsiffreeundospaceisavailable.
E.UndodatawillberetainedintheUNDOtablespacefor1，000seconds，thenitgetsmovedmovedtotheTEMPORARYtablespacetoprovidereadconsistency.

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单项选择题

YourCertkiller.comdatabaseisinARCHIVELOGmode.ThedatafilethatbelongstotheSYSTEMtablespacehasbecomecorrupted.Uptowhatpointcanyourecoverthedatabase？（）

A.Untillastcommit
B.Untilthetimeyouperformrecovery
C.Untilthetimethedatefilegotcorrupted
D.Untilthepointwherethelasttransactionbegun
E.YoucannotrecovertheSYSTEMtablespaceandmustre-createthedatabase.

单项选择题

Oneofthetablespacesisread－onlyinyourdatabase.Thelossofallcontrolfilesforcedyoutore－createthecontrolfile.Whichoperationdoyouneedtoperformafterre－creatingthecontrolfileandopeningthedatabase？（）

A.dropandre-createtheread-onlytablespaces
B.renametheread-onlydatafilestotheircorrectfilenames
C.changethetablespacestatusfromread/writetoread-only
D.re-createtheread-onlytablespacebecauseitisautomaticallyremoved