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RMAN backup types
Oracle Database Tips by Donald BurlesonMarch 22, 2015
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Question:
What are the RMAN backup types? I see RMAN differential, RMAN
cumulative and RMAN incremental backups, and I want to know the
differences in the types of RMAN backups.
Answer:
RMAN is very flexible and it offers many different types of backups.
We need to start with a list of backup types:
·
Full backup:
A full backup backs up all data files in the database, block-by-block, a
standalone backup with everything you need to recover to the point in time
when the full backup was collected.
·
Level 1 backup:
A level 1 backup includes only those blocks that have been changed since the
"parent" backup was taken. Remember a parent backup may be either a level 0
or a level 1 backup.
·
Level 0 backup:
A level 0 incremental backup is physically identical to a full backup and it
includes every data block in the file except empty blocks. 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.
·
Incremental backup:
An incremental backup can be either level 0 or level 1.
There are two types of
incremental backups, "differential" and "cumulative". See my full
notes on incremental differential vs. incremental cumulative backups.
·
Differential Incremental Backup:
When using differential incremental backup (the default type of incremental
backup), RMAN looks for changed data blocks which were changed after last
level 1 incremental backup. It there's no level 1 backup made before it, it
takes a backup of the changed data blocks which were made after level 0
incremental backup.
·
Cumulative
Incremental Backup:
In a cumulative incremental backup RMAN takes backup of all changed data
blocks after level 0 or level 1 incremental backup. Like a
differential backup, incremental backups also back up only the changed data
blocks, but an incremental backup only backs up the data that has changed
since the last backup. If the last backup was also an incremental
backup, the current incremental backups only records "changes to the
changes", a much smaller set of block changes, and hence, a much smaller
recovery time than a differential backup.
See my additional notes on
Incremental RMAN backups.
