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Scope: Core (OPC-10000-*) All specs

19 result(s) for Failover

OPC-10000-4 – OPC Unified Architecture - Part 4: Services

3.1.7 Failover

Failover act of switching the source or target of information. Note 1 to entry: In OPC UA redundant systems, a Failover is the act of a Client switching away from ... failed or degraded Server to another Server in the redundant set ( Server failover). In some cases a Client may have no knowledge of a Failover action occurring (transparent redundancy
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.1 General

general modes of Server Redundancy , transparent and non-transparent. In transparent Redundancy the Failover of Server responsibilities from one Server to another is transparent to the Client . The Client ... unaware that a Failover has occurred and the Client has no control over the Failover behaviour. Furthermore, the Client does not need to perform any actions to continue to send
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.2 RedundantServerSet Requirements

RedundantServerSets Clients shall be able to handle EventIds that are not synchronized. Following any Failover the Client shall call ConditionRefresh defined in OPC 10000-9 . Timestamp (Source/Server): If a Server
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.3.1 Client behaviour

appears as if it is just a single Server and the Client has no Failover actions to perform. All Servers in the RedundantServerSet have an identical ServerUri and an identical ... Client is not able to control which physical Server it actually connects to. Failover is controlled by the RedundantServerSet and a Client is also not able to actively Failover
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.3.2 Server requirements

functional Server will take over the Session and Subscriptions from the Failed Server . Failover may require a reconnection of the Client's SecureChannel but the EndpointUrl of the Server ... network. There may be custom hardware, where all components are redundant and Failover at a hardware level automatically. There may even be software based systems where all the transparency
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.1 Overview

RedundantServerSet and also Server information which tells the Client what modes of Failover the Server supports. This information allows the Client to determine what actions it may need to take ... order to accomplish Failover . This information is specified in NonTransparentRedundancyType ObjectType defined in OPC 10000-5 . The Servers in the non-transparent RedundantServerSet shall use the ServerCapability NTRS defined
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.2 ServiceLevel

highest ServiceLevel . Once connected, the ServiceLevel may change, but a Client shall not Failover to a different Server as long as the ServiceLevel of the Server is accessible
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.3 Load balancing

expected to connect to the Server with the highest ServiceLevel . Clients shall not Failover to a different Server in the RedundantServerSet of Servers as long as the Server
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.4 Server Failover modes

Server Failover modes The Failover mode of a Server is provided in the ServerRedundancy Object defined in OPC 10000-5 . The different Failover modes for non-transparent Redundancy are described ... Table 106 . Table 106 - Server Failover modes Name Description Cold Cold Failover mode is where only one Server can be active at a time. This may mean that redundant Servers
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.5.1 General

redundant Servers in the RedundantServerSet . The list is provided together with the Failover mode in the ServerRedundancy Object defined in OPC 10000-5 . To enable Clients to connect ... defines a list of Client actions for initial connections and Failovers . Table 107 - Redundancy Failover actions Failover mode and Client options Cold Warm Hot (a) Hot (b) HotAndMirrored On initial
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.5.2 Cold

Cold A Cold Failover mode is where the Client can only connect to one Server at a time. When the Client loses connectivity with the Active Server it will attempt ... action a Client would take if it is talking to a Server using Cold Failover mode. The monitor connection logic is defined in 6.7 . Figure 29 - Cold Failover NOTE There
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.5.3 Warm

Warm A Warm Failover mode is where the Client should connect to one or more Servers in the RedundantServerSet primarily to monitor the ServiceLevel . A Client can connect and create ... from all Servers . The Server with the highest ServiceLevel is the Active Server . For Failover the Client activates sampling and publishing on the Server with the highest ServiceLevel . Figure
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.5.4 Hot

Failover mode is where the Client should connect to two or more Servers in the RedundantServerSet and to subscribe to the ServiceLevel variable defined in OPC 10000-5 to find ... connected Server . Clients have the following choices for implementing Subscription behaviour in a Hot Failover mode: The Client connects to multiple Servers and establishes Subscription (s) in each where only
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.2.4.5.5 HotAndMirrored

HotAndMirrored A HotAndMirrored Failover mode is where a Client only connects to one Server in the RedundantServerSet because the Server will share this session/state information with the other Servers ... allows Clients to fail over without creating a new context for communication. On a Failover the Client will simply create a new SecureChannel on an alternate Server and then call
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.3 Client Redundancy

sufficient resources to buffer data during the change-over, data loss from a Client Failover can be prevented. OPC UA does not provide a standardized mechanism for conveying the SessionId
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.4.2 Transparent

This case is completely handled by the network infrastructure. The selected network path and Failover are transparent to the Client and the Server . Transparent network Redundancy is illustrated in Figure
OPC-10000-4 – OPC Unified Architecture - Part 4: Services

6.6.4.3 Non-Transparent

connections. In this case the Client is responsible for selecting the Endpoint and for Failover . For Failover the normal reconnect scenario described in 6.7 can be used. Only the SecureChannel
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

6.3.8 TransparentRedundancyType

serve it in different Sessions . The value of the CurrentServerId may change due to Failover or load balancing, so a Client that needs to track its data source shall subscribe
OPC-10000-5 – OPC Unified Architecture - Part 5: Information Model

6.3.15 NonTransparentBackupRedundancyType

defined in Table 24 . A Server represented by this Type shall use the Warm Failover mode defined in OPC 10000-4 . Table 24 - NonTransparentBackupRedundancyType definition Attribute Value BrowseName NonTransparentBackupRedundancyType IsAbstract ... HasProperty Variable RedundantServerArray RedundantServerDataType[] PropertyType Mandatory HasProperty Variable Mode RedundantServerMode PropertyType Mandatory HasComponent Method Failover The method has no parameters. Mandatory Conformance Units Redundancy Server The Mode Property represents