What is retention policy and what will happen to the restore points when retention policy is triggered?

Retention policy is a set of rules for retaining backup, copy and archive data to meet the legal and business needs of the organizations. The restore points which exceeded the limit of retention policy, deletion or merging of restore points will be performed to comply with the user defined retention policy.

Full backup job

Each restore point is independent, so deletion of restore points will be performed when the retention policy has been triggered. 

Differential backup job

Each differential restore point depends on the previous full restore point. When retention policy has been triggered, Vinchin Backup & Recovery will start deleting the earliest differential restore points, when all the differential restore points between the first and the second full restore points had been deleted, and when retention policy has been triggered for the next time, the first full restore point will be deleted.

Incremental backup job

When the retention policy of an incremental backup job has been triggered, Vinchin Backup & Recovery will try to merge the first incremental restore point with the full restore point on the first backup chain, the full restore point will step forward and the first incremental restore point will be gone. It will run the same process until all incremental restore points had been merged with the first full restore point. After that when the retention policy had been triggered for the next time, the first full restore point will be deleted, and then the second backup chain becomes the first and the restore point merging process goes on the same way.

Forever incremental backup job

Different from incremental backup, forever incremental backup will only create one backup chain for each VM included in the job, when retention policy has been triggered, Vinchin Backup & Recovery will merge the first incremental reatore point with the only full restore point at the beginning of the backup chain, and the timestamp of the full restore point will keep stepping forward each time when the incremental restore point had been merged.

In addition, If you implemented GFS retention policy  which is a long-term data retention policy, Vinchin backup & recovery will follow GFS retention policy first. Refers to What is GFS rentention policy for more information.