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 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 last backup taken . Remember a last 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”.
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
Full backup: A full backup backs up all data files in the database, block-by-block, a standalone backup with 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 last backup taken . Remember a last 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”.
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
No comments:
Post a Comment