本文为摘抄，目的为方便日后阅读：
http://docs.oracle.com/cd/B12037_01/server.101/b10734/rcmbackp.htm
To determine the archived logs needed for recovery of an online backup:
Start SQL*Plus and archive all unarchived logs, including the current log:
SQL> ALTER SYSTEM ARCHIVE LOG CURRENT;
Query V$LOG to determine the log sequence number of the current redo log, as in the following example (which includes output):
SQL> SELECT SEQUENCE# FROM V$LOG WHERE STATUS = 'CURRENT';
SEQUENCE#
----------
9100
Start RMAN and make an online backup of the database. For example, enter:
RMAN> BACKUP DATABASE;
Archive all unarchived logs, including the current log:
RMAN> SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';
In SQL*Plus, query V$LOG to determine the log sequence number of the current redo log:
SQL> SELECT SEQUENCE# FROM V$LOG WHERE STATUS = 'CURRENT';
SEQUENCE#
----------
9112
Back up the logs beginning with the first sequence number that you queried, and ending with the last sequence number minus 1. The log before the current log is the most recent archived log. For example, if the first query returned 9100, then start at 9100. If the second query returned 9112, then end at 9111.
For example, issue the following to back up the necessary archived logs:
RMAN> BACKUP ARCHIVELOG FROM SEQUENCE 9100 UNTIL SEQUENCE 9111;