If you restore the archived redo log files and data files, then you must perform media recovery before you can open the database. Any database transactions in the archived redo log files not reflected in the data files are applied to the data files, bringing them to a transaction-consistent state before the database is opened.
如果你恢复了归档的redo 日志文件和数据库文件，之后你必须在打开数据库之前执行介质恢复（Media Recovery）。一切在归档日志文件里的没有写到数据文件里的数据库交易记录将会被写入到数据文件中，以使数据库在打开之前保持数据一致性。
Media recovery requires a control file, data files (typically restored from backup), and online and archived redo log files containing changes since the time the data files were backed up. Media recovery is most often used to recover from media failure, such as the loss of a file or disk, or a user error, such as the deletion of the contents of a table.
介质恢复需要一个控制文件，数据文件（特别是从备份中恢复出来的）和online状态且归档的redo 日志文件，这个日志文件得包含自从数据文件备份以来产生的变化。介质恢复经常用来恢复介质失败，就像是文件和磁盘的丢失或者一个用户错误像是删除了一个表的内容。
Media recovery can be a complete recovery or a point-in-time recovery. Complete recovery can apply to individual datafiles, tablespaces, or the entire database. Point-in-time recovery applies to the whole database (and also sometimes to individual tablespaces, with automation help from Oracle Recover Manager (RMAN)).
介质恢复可以执行完全恢复和指定某个时间点的恢复（专业术语不是很清楚了），完全恢复可以应用于单个数据文件，表空间或整个数据库。而时间点恢复应用于整个数据库（有时也可以使用Oracle Recover Manager（RMAN）的自动化帮助来处理各个表空间）
In a complete recovery, you restore backup data files and apply all changes from the archived and online redo log files to the data files. The database is returned to its state at the time of failure and can be opened with no loss of data.
在完全恢复中，你要恢复备份的数据文件和将所有的归档日志和redo日志的变化应用到数据文件中。数据库会恢复到它失败时的那个状态，打开数据库时，不会有数据损失。
In a point-in-time recovery, you return a database to its contents at a user-selected time in the past. You restore a backup of data files created before the target time and a complete set of archived redo log files from backup creation through the target time. Recovery applies changes between the backup time and the target time to the data files. All changes after the target time are discarded.
在时间点恢复中，你将数据库的状态返回到用户选择的那个时间点。你从一个备份中恢复数据文件，这个数据文件是在你选择的时间点（目标时间）之前，而且必须有从之前的数据文件备份开始的完整的归档的redo日志文件。恢复将会应用数据文件从备份时间到目标时间的的所有改变。而在目标时间后的所有改变将会抛弃。
RMAN enables you to perform both a complete and a point-in-time recovery of your database. However, this documentation focuses on complete recovery.
RMAN允许你去执行完全恢复和基于时间点的恢复。
