Understanding Retention Period

When configuring a backup scheduler, you must specify the maximum time for which a backup can be held in your repository. If you have set a retention period of ‘x’ months, it ensures that the backup held in your repository only holds information of all changes made in the preceding ‘x’ months.

For SharePoint Online/OneDrive for Business items, retention period for items is calculated based on the date and time the item was modified.

For item versions, retention period is calculated based on the date and time at which the version was created.

When you configure a new backup scheduler, and you set a backup retention of ‘x’ months, the process that happens is as follows:

When the backup job begins, RecoveryManager Plus will analyze the metadata of all your SharePoint Online/OneDrive for Business data.
The retention period's starting point is set to the current date/time.
The last modification date of each item is identified
For SharePoint Online/OneDrive for Business items, the age of the item is calculated by comparing the last modified date and time and the current date/time. For item versions, the age is calculated by comparing the date and time at which the version was created and the current date/time.
The age is then compared with the value that you’ve set as the maximum retention period.
If the age of an item exceeds the specified interval, the item will not be backed up into the repository.
If the age is less than the specified retention period, the item will be backed up.

For example, assume a backup scheduler is created on July 5, 2018 to perform a backup every Sunday at 12:00 AM. The retention period is set to 1 year. The first time that the scheduler will run is on July 8th, 2018 at 12:00 AM. July 8th, 2018 will be set as the starting point of the retention period. All SharePoint Online/OneDrive for Business items that have their last modified entry from July 8, 2017 to July 8, 2018 will be backed up as the age of the modified item will be less than the maximum retention period. Any item that has the last modified date earlier than July 8, 2017 will not be backed up.

This retention policy is then applied to the backed up data on the repository.

After all items that satisfy the age criteria are backed up, RecoveryManager Plus checks for items that have exceeded the retention period.
Items whose age exceeds the retention period will be removed from the backup repository.

Considering the same example from the scenario above, the next instalment of the backup will occur on July 15th, 2018 at 12:00 AM. With July 15th, 2018 set as the starting point of the retention period, RecoveryManager Plus will scan the backed up data to find all items whose last modified time are earlier than July 15th, 2017. All items that fit the criteria are then removed from the repository.