A GlobalDiscoveryServeris an OPC UA Serverimplementing different global services for discovery, Certificatemanagement, user or PubSub key management, user authorization, software and device management.

The number of OPC UA Applicationsusing the different services as OPC UA Clientmay be huge and the OPC UA Serveris most likely not able to handle connections from all OPC UA Clientsat the same time. Therefore an OPC UA Clientconnected to a GDS should minimize the time it is connected to the GDS to the currently required actions. The OPC UA Clientshall disconnect as soon as it completes the sequence of actions needed to interact with the services. The OPC UA Clientsshall not keep connections open between the execution of sequences.

A GDS OPC UA Serveris allowed to close Sessionswith OPC UA Clients not authenticated as one of the GDS administrative Rolesif it runs out of connection resources. If the GDS needs to close Sessions, it should first close Sessionswithout GDS management Privileges. Otherwise it may close the Sessionthat was inactive for the longest time not using GDS global services e.g. Methodcalls.

It is also recommended to use a short maximum session timeout on the GDS OPC UA Server.

Actions performed cyclically by OPC UA Applicationsduring PullManagementshall start the second cycle with a random delay that is between one and at least ten percent of the cycle period.