The mechanism of Oracle Incremental backup

There are two types of incremental backups in Rman: Differential and cumulative, and the levels of backups are divided into 0, 1, 2, 3, 4, 5 levels, with the highest level of 0.

Differential backup differential (for superior and even peer backups are accepted):

Parsing: The 0-level backup (full backup) created in the Sunday, the 2-level incremental backup created in Monday, is backed up only after the backup created in Sunday, and the modified block of data that occurs at the current moment. Tuesday is also an incremental backup, so you only need to back up the data blocks that were modified after the backup set that was created in Monday. By Wednesday, the level 1 backup that was created must be backed up to all the changes that occurred after the Sunday backup operation. Thursday, Friday, and Saturday are all Level 2 backups that only need to be backed up by the modifications that occurred the day before the backup operation. Until Sunday recreate a new 0-level backup, reciprocating.

Cumulative incremental backup cumulative (approval only for superior backups):

Resolution: The same is the 0-level incremental backup created in Sunday, create a 2-level incremental backup in Monday, or 2-level incremental backups in Tuesday, but when you create an incremental backup in Tuesday, you will not take care of the 2-level incremental backup of the previous day, but all of the modified blocks of data are backed up after the backup operation in Sunday. The 1-level backup, created in Wednesday, is also a premium backup only, and it starts with a change from the previous Sunday backup. By analogy, the 2-level incremental backup created in Thursday is based on an incremental backup of Wednesday. Friday and Saturday are also 2-level incremental backups, but they also ignore incremental backups created the previous day, directly based on the Wednesday 1-level incremental backup, and back up the changes that occurred after Wednesday until Sunday, another level 0 backup.

Attention:

1, the backup command does not display the specified case, the default differential. However, from a recovery-efficiency perspective, cumulative backups perform well and do not need to read too many backup sets.

2, if the beginning is not a level 0 backup, other non-level 0 backup level will be automatically created.

3, oracle10g before the incremental backup has 0, 1, 2, 3, 4 levels.

4, the official documents in the ORACLE10G only 0, 12 levels, but the actual execution can still specify multiple levels.