Synthetic full backup has two kinds of backup levels:
- synth_full – performs synthetic full backup and combines the latest full backup with all subsequent incremental backups into a new full backup.
- incr_synth_full – performs a new incremental backup and then generate synthetic full backup immediately. This can ensure the status of the save set is up-to-date.
To better understand synth_full and incr_synth_full, I’d like to explain more.
synth_full can only back up the status of save set the last time when performing incremental backup. If any change is made after the latest incremental backup, synth_full will not back up it. In order to back up the latest status of save set, you should choose incr_synth_full. It will perform an incremental backup on the basis of the latest incremental backup and then combine the incremental backup with the latest full backup and all subsequent incremental backups.
For example, we perform a full backup on Sunday 9:00 am and perform incremental backups on Monday, Tuesday and Wednesday 9:00 am.
If we perform synth_full on Wednesday 2:00 pm, it will combine the full backup of Sunday with three subsequent incremental backups into a Synthetic full backup. The status of save set is its status on Wednesday 9:00 am. If the save set was modified on Wednesday 1:00 pm, synth_full will not back up its status at that time.
However, if we perform incr_synth_full, it will perform an incremental backup to back up the current status (Wednesday 2:00 pm) first and then combine this incremental backup with the full backup of Sunday and three subsequent incremental backups into a Synthetic full backup. This ensures the status of save set is latest when performing a synthetic full backup.