Versioning
When the persistence mode is enabled, the objects that are local to a user (that is, the objects that are not yet deployed to an agent) are versioned.
A version check is performed when you try to save a local object. The save operation succeeds only if the version is the latest. Otherwise, you get an exception that asks you to refresh your copy. It can happen only if the same user logs in from two sessions.
For agent deployed objects or common objects, versioning is not maintained. This is because Agents do not support versioning and version based deployment of configuration objects.