在RMAN的备份中，有分冷备份，热备份；全备份，增量备份；而增量备份里又分差异增量备份与累积增量备份。
我们先来一一了解这几个备份的含义：
冷备份 - 即关闭数据库之后备份所有的关键性文件，包括数据文件、控制文件、联机文件，如果数据库是处于归档模式下，配合归档日志文件，可以更好的恢复数据。这种备份说直白点就是物理备份，复制粘贴的操作。
热备份 - 即数据库处于运行状态下，以ARCHIVE方式备份数据库的方法。既然是以ARCHIVE方式备份，那么数据库就必须处于归档模式下。
关于全备份与增量备份，官方的解释是：
Full
A backup of a datafile that includes every allocated block in the file being backed up. A full backup of a datafile can be an image copy, in which case every data block is backed up. It can also be stored in a backup set, in which case datafile blocks not in use may be skipped, according to rules in Oracle Database Backup and Recovery Reference.
A full backup cannot be part of an incremental backup strategy; that is, it cannot be the parent for a subsequent incremental backup.
Incremental
An incremental backup is either a level 0 backup, which includes every block in the file except blocks compressed out because they have never been used, or a level 1 backup, which includes only those blocks that have been changed since the parent backup was taken.
A level 0 incremental backup is physically identical to a full backup. The only difference is that the level 0 backup is recorded as an incremental backup in the RMAN repository, so it can be used as the parent for a level 1 backup.
大致意思就是全备份与增量备份中的0级备份都是全备份，但是它们又有点不同，全备份不能作为增量备份的基础，全备份是备份了used and unused block，而0级备份只是备份used block。
所以，我们建议每年或半年要进行一次全备份。使用增量备份可以根据自已数据库的大小，磁盘空间等因素，综合考虑备份策略。
差异增量(Differential)：是备份上级及同级备份以来所有变化的数据块，是默认增量备份方式。该方式备份时间短，但恢复时间会更长。
累积增量(Cumulative)：是备份上级备份以来所有变化的块。该方式正好与差异增量备份相反，它所需的备份时间会更长，但恢复时间短。
最后，增量备份是以0级备份为基础的，如果你没有进行0级备份，而是直接进行1级或2级备份，那么它们会非常恪尽职守的帮助你顺带一起备份了。
好了，说了一大堆，小伙伴们应该有所收获吧⊙⊙
