Your database is running in ARCHIVELOG mode. You are performing a user-managed backup of the DATA1 tablespace. You place the DATA1 tablespace in backup mode by issuing the following statement:
ALTER TABLESPACE data1 BEGIN BACKUP;
While you are performing the backup, an error occurs that causes the instance to terminate abnormally.
Which statement about the DATA1 tablespace is true?
A. The DATA1 tablespace is automatically taken out of backup mode when the instance aborts.
B. If you restart the database, the DATA1 tablespace will be automatically taken out of backup mode when the database is opened.
C. If you restart the database, the DATA1 tablespace will be automatically taken out of backup mode when the database is mounted.
D. If you restart the database, the database will not be opened.
backup mode不能启动数据库，Alter tablespace data1 end backup;alter databse end backup;
原文：http://www.cnblogs.com/Babylon/p/7845263.html