Helium implements a default change tracking strategy for persistent objects. This change tracking strategy generates change logs that is used by the Helium / Journey middleware to synchronise objects between Helium and Journey applications. The change logs can also be used as a basic audit trail.

The @NotTracked object annotation designates an object should not be considered for Helium's default change tracking. In general, persistent objects that should not be considered for change tracking and therefore not form part of audit logs should be annotated with the @NotTracked annotation. A good example of where this might be applicable is for objects that are themselves used by DSL applications for audit logs or similar.

Persistent objects that are not intended to sync to the Journey application's database should rather be included in the middleware's "Change Log Skip Tables". More information on this difference in intention can be found here: https://wiki.mezzanineware.com/display/HTUT/Change+Tracking+and+Syncing