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BACKUP DATABASE and BACKUP INCREMENTAL LEVEL 0 DATABASE backups have the same contents, but they still differ. Full backup is not applied to incremental backup policies, only level 0 backups can be used as base points for incremental backups, and there is no RMAN command to translate the relationship between the two. When the database is open, incremental backup can only be used if the database is in archive mode. If the database is not in archive mode and the database is in open state, incremental backup cannot be used.

There are two types of incremental backups: cumulative incremental and differential incremental

Accumulate incremental backups

An incremental backup that backs up all the blocks changed since the most recent backup at level 0. When recovering with cumulative incremental backups, only the most recent cumulative incremental backup must be applied.

Cumulative incremental backups back up all changed blocks from the most recent level 0 backup point to the present, and only the most recent incremental backups are used when restoring data using incremental backups

differential incremental backup

A type of incremental backup that backs up all blocks that have changed since the most recent backup at level 1 or level 0. For example, in a differential level 1 backup RMAN determines which level 1 or level 0 incremental backup is most recent and then backs up all blocks changed since that backup. Differential backups are the default type of incremental backup. When recovering using differential incremental backups, RMAN must apply all differential incremental level 1 backups since the restored data file backup.

Differential incremental backups back up all changed blocks from the most recent level 0 or 1 point up to the present. When there is only a level 0 backup before, differential incremental backup will only backup the changed blocks from level 0 to the present. When there is a level 1 backup before, differential incremental backup will backup the changed blocks from level 1 to the present. When restoring data using differential incremental backups, all level 1 differential incremental backups need to be applied.

Difference between differential and cumulative backups

Differential backups save more space and resources than cumulative backups, but level 1 availability must be guaranteed to ensure that the database cannot be restored to the point of failure because of the effectiveness of a certain level 1. In contrast, cumulative backups are more secure than differential backups because their own backups are repetitive, and only the most recent level 1 backup needs to be available to recover to the point of failure, rather than all level 1 backups. Accumulating backups also requires more disk space.

RMAN> backup incremental level 0 database;

Starting backup at 2017-07-30 13:12:44

using channel ORA_DISK_1

channel ORA_DISK_1: starting incremental level 0 datafile backup set

channel ORA_DISK_1: specifying datafile(s) in backup set

input datafile file number=00001 name=/u01/app/oracle/oradata/test/system01.dbf

input datafile file number=00002 name=/u01/app/oracle/oradata/test/sysaux01.dbf

input datafile file number=00004 name=/u01/app/oracle/oradata/test/users01.dbf

input datafile file number=00003 name=/u01/app/oracle/oradata/test/undotbs01.dbf

channel ORA_DISK_1: starting piece 1 at 2017-07-30 13:12:44

channel ORA_DISK_1: finished piece 1 at 2017-07-30 13:12:59

piece handle=/home/oracle/1csal8ic_1_1 tag=TAG20170730T131244 comment=NONE

channel ORA_DISK_1: backup set complete, elapsed time: 00:00:15

channel ORA_DISK_1: starting incremental level 0 datafile backup set

channel ORA_DISK_1: specifying datafile(s) in backup set

including current control file in backup set

including current SPFILE in backup set

channel ORA_DISK_1: starting piece 1 at 2017-07-30 13:13:02

channel ORA_DISK_1: finished piece 1 at 2017-07-30 13:13:03

piece handle=/home/oracle/1dsal8ir_1_1 tag=TAG20170730T131244 comment=NONE

channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01

Finished backup at 2017-07-30 13:13:03

change data

SQL> create table scott.backuptest(a int);

Table created.

SQL> insert into scott.backuptest values(1);

1 row created.

SQL> commit

2 /

Commit complete

Level 1 Cumulative Incremental Backup

RMAN> BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE;

Starting backup at 2017-07-30 13:25:38

using target database control file instead of recovery catalog

allocated channel: ORA_DISK_1

channel ORA_DISK_1: SID=1 device type=DISK

channel ORA_DISK_1: starting incremental level 1 datafile backup set

channel ORA_DISK_1: specifying datafile(s) in backup set

input datafile file number=00001 name=/u01/app/oracle/oradata/test/system01.dbf

input datafile file number=00002 name=/u01/app/oracle/oradata/test/sysaux01.dbf

input datafile file number=00004 name=/u01/app/oracle/oradata/test/users01.dbf

input datafile file number=00003 name=/u01/app/oracle/oradata/test/undotbs01.dbf

channel ORA_DISK_1: starting piece 1 at 2017-07-30 13:25:39

channel ORA_DISK_1: finished piece 1 at 2017-07-30 13:25:46

piece handle=/home/oracle/1fsal9aj_1_1 tag=TAG20170730T132538 comment=NONE

channel ORA_DISK_1: backup set complete, elapsed time: 00:00:07

channel ORA_DISK_1: starting incremental level 1 datafile backup set

channel ORA_DISK_1: specifying datafile(s) in backup set

including current control file in backup set

including current SPFILE in backup set

channel ORA_DISK_1: starting piece 1 at 2017-07-30 13:25:47

channel ORA_DISK_1: finished piece 1 at 2017-07-30 13:25:48

piece handle=/home/oracle/1gsal9aq_1_1 tag=TAG20170730T132538 comment=NONE

channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01

Finished backup at 2017-07-30 13:25:48

v$backup_datafile view to view backups

SQL> SELECT FILE#, INCREMENTAL_LEVEL, COMPLETION_TIME,

BLOCKS, DATAFILE_BLOCKS

FROM V$BACKUP_DATAFILE

WHERE INCREMENTAL_LEVEL IN (0,1)

ORDER BY COMPLETION_TIME; 2 3 4 5

FILE# INCREMENTAL_LEVEL COMPLETION_TIME BLOCKS DATAFILE_BLOCKS

---------- ----------------- ------------------- ---------- ---------------

3 0 2017-07-30 13:12:44 1241 11520

4 0 2017-07-30 13:12:49 49665 52320

2 0 2017-07-30 13:12:52 62449 81920

1 0 2017-07-30 13:12:53 78054 117760

3 1 2017-07-30 13:25:40 160 11520

4 1 2017-07-30 13:25:42 11 52320

2 1 2017-07-30 13:25:43 527 81920

1 1 2017-07-30 13:25:44 53 117760

8 rows selected.

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