Locking is the means to avoid concurrent modifications to a TopologyElement or Network and their components. Clients shall use the locking services if they need to make a set of changes (for example, several Write operations and Method invocations) and where a consistent state is available only after all of these changes have been performed. The main purpose of locking a TopologyElement is avoiding concurrent modifications. The main purpose of locking a Network is avoiding concurrent topology changes.

A lock from one Client usually allows other Clients to view (navigate/read) the locked element. Servers may choose to implement an exclusive locking where other Clients have no access at all (e.g. in cases where even read operations require certain settings in a TopologyElement).

When locking a TopologyElement, the lock applies to the complete TopologyElement (including all components such as blocks or modules).

Servers may allow independent locking of component TopologyElements, if no lock is applied to the top-level TopologyElement.

If the Online/Offline model is supported (see 7.3), the lock always applies to both the online and the offline version.

When locking a Network, the lock applies to the Network and all connected TopologyElements. If any of the connected TopologyElements provides access to a sub-ordinate Network (like a gateway), the sub-ordinate Network and its connected TopologyElements are locked as well.