ORACLE Rman Backup from original source- -The policy instance diagram of differential increment and cumulative increment
The backup command, when not explicitly specified, chooses the differential method, the differential incremental backup, by default. However, from the perspective of recovery efficiency, the cumulative mode of incremental backup performance better, after all, do not need to read so many backup sets.
Attention:
in the 10g in previous versions, incremental backups could have more than n levels, from level 0, Level 1, and Level 2 ... This is ordered until the N-level (n is a positive integer less than or equal to 4).
In the 10g release, Oarcle's official documentation clearly states that incremental backups are only 0 and 12 levels (too many incremental levels are not really significant), but when you actually perform incremental operations, you can still specify multiple levels, which can support up to 4 levels of incremental backups.
Version 10g for an example of the 0,1 difference and cumulative incremental backup strategy is shown below:
ORACLE Rman Backup--a policy instance diagram of Delta and cumulative increments