单项选择题 In your Certkiller .com production database， you find that the database users are able to create and read files with unstructured data， available in any location on the host machine from an application.  You want to restrict the database users to access files in a specific location on the host machine.  What could do to achieve this？（）

单项选择题 YouworkasadatabaseadministratorforCertkiller.com.Yourdatabaseisconfiguredforautomaticundomanagement.UNDO_RETENTIONissetto3hours.Youwanttoflashbackatablethatwascreatedlastyear.Howfarbackcantheflashbackquerygo？（）

单项选择题 The operating system filecratabin the Linux platform gets updated whenever you create a new database on the same host machine.  What kind of information is stored is stored in this file？（）