This management feature enables Alfresco ECM to track user usages within the DM repository. It also allows admins to, optionally, set user quotas.
Alfresco will maintain user usages for content created/owned by the user.
The usage is based on the content size (in bytes) and is typically displayed in Kb, Mb or Gb
The current usage is shown in Alfresco Explorer or Alfresco Share (since 3.2), on the user profile/settings page
The usage is also listed on the 'Maintain System Users' admin page (Alfresco Explorer)
The usages are maintained for a given store (or set of stores) which by default is configured to workspace://SpacesStore
The admin user can optionally set quotas for a given user.
These can be set using Alfresco Explorer or Alfresco Share (since 3.2) when creating/editing user details, and are also listed on the 'Maintain System Users' admin page (Alfresco Explorer)
If a user tries to add or edit content (via any repository interface) such that usage will exceed their current quota then the user will see an error message such as: 'User quota exceeded'
Is it possible for a user to have a usage that is greater than their quota ?
Yes, under certain circumstances. For example, an administrator may lower a user's quota such that it is below their current usage.
If I measure the physical size of the content store then there appears to be a slight discrepancy compared to the total user usages ?
The internal 'System' account is not currently defined as a person in Alfresco and hence does not appear in the 'Maintain System Users' page. The 'System' account will typically create some items when bootstrapping a new repository. For the time being these 'System' usages are maintained which can lead to a slight discrepancy.