545.When performing an online backup, what is the proper order of the following steps?
A. Issue the alter database end backup command.
B. Back up the archived redo logs.
C. Issue the alter database begin backup command.
D. Back up the database files.
E. Determine the beginning log sequence number.
F. Determine the ending log sequence number.
G. Force a log switch with the alter system switch logfile command.
H. a, b, c, d, e, f, g
I. c, d, a, b, e, g, f
J. f, d, b, g, a, c, e
K. e, c, d, a, g, f, b
L. a, f, b, g, e, c, d
Answer: D
答案解析：
可参考550题：http://blog.csdn.net/rlhua/article/details/14983295
记下开始的日志序列号
然后开始备份数据库
sys@TEST1107> alter database begin backup;
Database altered.
开始讲数据库置为备份状态
OS级拷贝文件
结束数据库的备份状态
sys@TEST1107> alter database end backup;
Database altered.
切换日志，使日志归档
sys@TEST1107> alter system switch logfile;
System altered.
记下结束的日志序列号
在OS级别拷贝归档日志文件