Each update to the repository creates a new content revision. As a result, with each update the size of the repository grows. To avoid uncontrolled repository growth, old revisions need to be be cleaned up to free disk resources. This maintenance functionality is called Revision Cleanup. It has been available as an offline routine since AEM 6.0.
With AEM 6.3 an online version of this functionality called Online Revision Cleanup was introduced. Compared to Offline Revision Cleanup where the AEM instance has to be shut down, Online Revision Cleanup can be run while the AEM instance is online. Online Revision Cleanup is turned on by default and it is the recommended way of performing a revision cleanup.
How to Run Online Revision Cleanup
Online Revision Cleanup is configured by default to automatically run once a day on both AEM Author and Publish instances. All you need to do is define the maintenance window during a period with the least user activity.
Running Online Revision Cleanup After Offline Revision Cleanup
The revision cleanup process reclaims old revisions by generations. This means that each time you run revision cleanup a new generation is created and kept on the disk. There is a difference however between the two types of revision cleanup: offline revision cleanup keeps one generation while online revision cleanup keeps two generations.