单项选择题 You have lost datafiles 1 and 3 from your database，and the database has crashed.  In what order should you perform the following steps to recover your database？（） 1. Take the datafiles that were lost offline.  2. startup mount the database  3. Issue the alter database open command. 4. Restore the datafiles that were lost  5. Recover the datafiles with the recover datafile command. 6. Bring the datafiles back online.  7. Recover the database with the recover database command.

单项选择题 Ifalogfilebecomescorrupted，itmaycausethedatabasetostall.Howwouldyoucorrectsuchasituation？（）

单项选择题 Whenyoucreateabackupcontrolfile，whereistheresultingfilewrittento？（）