Incremental backups can be either level 0 or level 1. A level 0 incremental backup, which is the base for subsequent incremental backups, copies all blocks containing data, backing the datafile up into a backup set just as a full backup would. The only difference between a level 0 incremental backup and a full backup is that a full backup is never included in an incremental strategy.
A level 1 incremental backup can be either of the following types:
A differential backup, which backs up all blocks changed after the most recent incremental backup at level 1 or 0.
RMAN> BACKUP INCREMENTAL LEVEL 1 DATABASE;
A cumulative backup, which backs up all blocks changed after the most recent incremental backup at level 0.
RMAN> BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE; # blocks changed since level 0
