Buffering during client restart

To use buffered values after a restart of the OPC UA client or a reactivation of the connection to the OPC UA server, the old subscription can be transferred to the new session (OPC UA service "transferSubscription"). Buffered values are only available if the following requirements are met:

• The subscription must exist on the server, which means the subscription timeout (see Buffering during connection loss) must not be expired.

• The option "persistent" must be enabled for the respective subscriptions, otherwise the client does not save the necessary information for reusing the subscription after connecting to the server.

• The session must be established with the same user name and password in order to transmit the subscription of a previous session to the current one. User name and password are required for the involved session. The transfer of subscriptions is not possible for anonymous authentication.

• During the time the OPC UA client is stopped or not connected, the configuration of the subscription must not be changed. The client stores the configuration when saving the subscription information. If the configuration does not match when loading the subscription information, new subscriptions are created.

Note

The buffer must be defined big enough for the downtime. Refer to Buffering during connection loss for further information on monitored items etc.