As soon as you discover that you have lost an online redo log， if the database is still functioning， what should be your first action？（）  

单项选择题Your database has experienced a loss of datafile users_01.dbf， which is associated with a ablespace called USERS.  The database is still running.  Which answer properly describes the rder of the steps that you would use to recover from this error？（）   a. Shut down the database.  b. Take the users_01.dbf datafile offline with the alter database command.  c. Restore the users_01.dbf datafile from backup media with the required archived redo logs.  d. Restore all users tablespace-related datafiles from backup media. e. Issue the recover tablespace users command. f. Issue the recover datafile users_01.dbf command. g. Start up the database.  h. Bring the users_01.dbf datafile online with the alter database command.

A.a， c， f， g
B.b， c， f， h
C.a， b， c， f， g
D.a， b， c， f， g， h
E.b， c， f， e， g

单项选择题Yourarchive-logdestinationdirectoryrunsoutofspace.Whatistheimpactofthisonthedatabase？（）

A. None. The database will switch over to the stand-by archive-log destination directory.
B. A warning message will be written to the alert log of the database，but no adverse impacts to the database will be experienced.
C. The database will shut down，and will not restart until you correct the out-of-space situation.
D. The database will continue to try to write to the archive-log destination directory for one hour. After one hour，the database will shut down normally.
E. Once Oracle has cycled through all online redo logs，it will stop processing any DML or DDL until the out-of-space condition is corrected.