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6.3 ObjectTypes for the Server Object ToC Previous Next

6.3.1 ServerType ToC Previous Next index

This ObjectType defines the capabilities supported by the OPC UA Server. It is formally defined in Table 9.

Table 9 – ServerType Definition

Attribute Value
BrowseName ServerType
IsAbstract False

Subtype of the BaseObjectType defined in 6.2

References NodeClass BrowseName DataType / TypeDefinition Modelling Rule
HasProperty Variable ServerArray String[]
PropertyType
Mandatory
HasProperty Variable NamespaceArray String[]
PropertyType
Mandatory
HasProperty Variable UrisVersion VersionTime
PropertyType
Optional
HasComponent Variable ServerStatus1 ServerStatusDataType
ServerStatusType
Mandatory
HasProperty Variable ServiceLevel Byte
PropertyType
Mandatory
HasProperty Variable Auditing Boolean
PropertyType
Mandatory
HasProperty Variable EstimatedReturnTime DateTime
PropertyType
Optional
HasProperty Variable LocalTime TimeZoneDataType
PropertyType
Optional
HasComponent Object ServerCapabilities1 -
ServerCapabilitiesType
Mandatory
HasComponent Object ServerDiagnostics1 -
ServerDiagnosticsType
Mandatory
HasComponent Object VendorServerInfo -
VendorServerInfoType
Mandatory
HasComponent Object ServerRedundancy1 -
ServerRedundancyType
Mandatory
HasComponent Object Namespaces -
NamespacesType
Optional
HasComponent Method GetMonitoredItems Defined in 9.1 Optional
HasComponent Method ResendData Defined in 9.2 Optional
HasComponent Method SetSubscriptionDurable Defined in 9.3 Optional
HasComponent Method RequestServerStateChange Defined in 9.4 Optional
NOTE Containing Objects and Variables of these Objects and Variables are defined by their BrowseName defined in the corresponding TypeDefinitionNode. The NodeId is defined by the composed symbolic name described in 4.1.        

ServerArray defines an array of Server URIs. This Variable is also referred to as the server table. Each URI in this array represents a globally-unique logical name for a Server within the scope of the network in which it is installed. Each OPC UA Server instance has a single URI that is used in the server table of other OPC UA Servers. Index 0 is reserved for the URI of the local Server. Values above 0 are used to identify remote Servers and are specific to a Server. OPC 10000-4 describes discovery mechanism that can be used to resolve URIs into URLs. The Server URI is case sensitive.

The URI of the ServerArray with Index 0 shall be identical to the URI of the NamespaceArray with Index 1, since both represent the local Server.

The indexes into the server table are referred to as server indexes or server names. They are used in OPC UA Services to identify TargetNodes of References that reside in remote Servers. Clients may read the entire table or they may read individual entries in the table. The Server shall not modify or delete entries of this table while any client has an open session to the Server, because clients may cache the server table. A Server may add entries to the server table even if clients are connected to the Server.

NamespaceArray defines an array of namespace URIs. This Variable is also referred as namespace table. The indexes into the namespace table are referred to as NamespaceIndexes. NamespaceIndexes are used in NodeIds in OPC UA Services, rather than the longer namespace URI. Index 0 is reserved for the OPC UA namespace, and index 1 is reserved for the local Server. Clients may read the entire namespace table or they may read individual entries in the namespace table. The Server shall not modify or delete entries of the namespace table while any client has an open session to the Server, because clients may cache the namespace table. A Server may add entries to the namespace table even if clients are connected to the Server. It is recommended that Servers not change the indexes of the namespace table but only add entries, because the client may cache NodeIds using the indexes. Nevertheless, it might not always be possible for Servers to avoid changing indexes in the namespace table. Clients that cache NamespaceIndexes of NodeIds should always check when starting a session to verify that the cached NamespaceIndexes have not changed.

UrisVersion defines the version of the ServerArray and the NamespaceArray. Everytime the ServerArray or the NamespaceArray is changed, the value of the UrisVersion shall be updated to a value greater than the previous value. The UrisVersion Property is used in combination with the SessionlessInvoke Service defined in OPC 10000-4. If a Server supports this Service, the Server shall support this Property. It is the responsibility of the Server to provide a consistent set of values for the ServerArray, NamespaceArray and the UrisVersion Properties. The VersionTime DataType is defined in OPC 10000-4.

ServerStatus contains elements that describe the status of the Server. See 12.10 for a description of its elements.

ServiceLevel describes the ability of the Server to provide its data to the client. The value range is from 0 to 255, where 0 indicates the worst and 255 indicates the best. OPC 10000-4 defines required sub-ranges for different scenarios. The intent is to provide the clients an indication of availability among redundant Servers.

Auditing is a Boolean specifying if the Server is currently generating audit events. It is set to TRUE if the Server generates audit events, otherwise to false. The Profiles defined in OPC 10000-7 specify what kind of audit events are generated by the Server.

EstimatedReturnTime indicates the time at which the Server is expected to have a ServerStatus.State of RUNNING_0. A Client that observes a shutdown or a ServiceLevel of 0 should either wait until after this time to attempt to reconnect to this Server or enter into slow retry logic. For example, most Clients will attempt to reconnect after a failure immediately and then progressively increase the delay between attempts until some maximum delay. This time can be used to trigger the Client to start its reconnect logic with some delay.

LocalTime is a structure containing the Offset and the DaylightSavingInOffset flag. The Offset specifies the time difference (in minutes) between the Server time in UTC and the local time at the Server location. If DaylightSavingInOffset is TRUE, then Standard/Daylight savings time (DST) at the Server location is in effect and Offset includes the DST correction. If FALSE then the Offset does not include DST correction and DST may or may not be in effect.

ServerCapabilities defines the capabilities supported by the OPC UA Server. See 6.3.2 for its description.

ServerDiagnostics defines diagnostic information about the OPC UA Server. See 6.3.3 for its description.

VendorServerInfo represents the browse entry point for vendor-defined Server information. This Object is required to be present even if there are no vendor-defined Objects beneath it. See 6.3.6 for its description.

ServerRedundancy describes the redundancy capabilities provided by the Server. This Object is required even if the Server does not provide any redundancy support. If the Server supports redundancy, then a subtype of ServerRedundancyType is used to describe its capabilities. Otherwise, it provides an Object of type ServerRedundancyType with the Property RedundancySupport set to none. See 6.3.7 for the description of ServerRedundancyType.

Namespaces provides a list of NamespaceMetadataType Objects with additional information about the namespaces used in the Server. See 6.3.14 for the description of NamespaceMetadataType.

The GetMonitoredItems Method is used to identify the MonitoredItems of a Subscription. It is defined in 9.1; the intended usage is defined in OPC 10000-4.

The ResendData Method is used to get the latest values of the data monitored items of a Subscription. It is defined in 9.2; the intended usage is defined in OPC 10000-4.

The SetSubscriptionDurable Method is used to set a Subscription into a mode where MonitoredItem data and event queues are stored and delivered even if an OPC UA Client was disconnected for a longer time or the OPC UA Server was restarted. It is defined in 9.3; the intended usage is defined in OPC 10000-4.

The RequestServerStateChange Method allows a Client to request a state change in the Server. It is defined in 9.4; the intended usage is defined in OPC 10000-4.

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