RMAN incremental and cumulative incremental

1. Concepts

Difference increment (differential): All data blocks that have changed since the backup of a low-level or the same-level backup. This refers to the differential data blocks that need to be backed up since the preliminary backup.

1. If both the low-level and the same-level Backup existsRecent low level (n-1)Changed data blocks.

2. If there is no n-1 backup, select backupSame LevelData blocks changed since the backup.

3. If there is no backup of the same level, the backupLower level (n-x)Changed data.

4. If there are both N-1 and the same level, backupSame LevelData that has changed since then.

Cumulative): All data blocks changed since the n-1 level (upper level) or lower level are backed up.

1. If both the low level and n-1 level exist in the preceding backup, the backup fromN-1LevelChanged data blocks.

2. If there is no n-1 level, the standbyLower level (n-x ).

2. Backup policy and recovery

Taking RMAN multi-level Incremental backup as an example of a backup policy: Incremental Backup requires a level 0 backup as the basis. The difference between level 0 backup and full backup is that level 0 backup can be used for incremental recovery, full backup is not supported.

Backup policy: we make the following backup policy for a week

Case.
Week
Incremental variance
Cumulative Increment

Sunday
Level 0
Level 0

Monday
Level 2
Level 2

Tuesday
Level 2
Level 2

Wednesday
Level 1
Level 1

Thursday
Level 2
Level 2

Friday
Level 2
Level 2

Saturday
Level 2
Level 2

Sunday
Level 0
Level 0

For incremental differences, data changed from Sunday to Monday for secondary standby on Monday (no n-1 or the same level)

Data changed from Monday to Tuesday for secondary backup on Tuesday (no n-1 level, with the same level)

Data changed from Sunday to Wednesday for level-1 backup on Wednesday (neither level-1 nor level-1)

Data of second-level backup changes on Thursday from Wednesday to Thursday (with n-1 levels)

Data changed from the second-level backup on Friday from Thursday to Friday (with n-1 levels, with the same level)

Data changes in the secondary standby mode on Saturday from Friday to Saturday (with n-1 levels, with the same level)

If the database needs to be restored on Saturday (the secondary backup is completed on Friday, and the standby database is not backed up on Saturday), the incremental, the second-level archiving logs on Thursday and Friday can be completely restored.

For cumulative incremental data, the secondary standby data on Monday changes from Sunday to Monday (there are no n-1 levels, there are lower levels ).

Data on Tuesday secondary backup changes from Sunday to Tuesday (no n-1 level, lower level ).

Data on the first-level backup on Wednesday from Sunday to Wednesday (with n-1 levels ).

Data of second-level secondary backup changes from Wednesday to Thursday (with n-1 levels ).

Data of the second-level backup on Friday changes from Wednesday to Friday (with n-1 levels ).

Data on the second-level backup on Saturday changes from Wednesday to Saturday (with n-1 levels ).

Description:

If the database needs to be restored on Saturday (the secondary backup is completed on Friday, and the incremental data is not backed up on Saturday), the incremental data must be level 0 on Sunday and Level 1 on Wednesday, on Friday, the second-level archiving log can be completely restored.

Typical backup policy cases:

Perform a full backup of the database every six months (including all data and read-only tablespaces ).
Perform a zero-level backup every month (excluding the read-only tablespace ).
Perform a level-1 backup every week.
Perform a secondary backup every day.