lmxopcua/docs/HistoricalDataAccess.md

Historical Data Access

LmxNodeManager exposes OPC UA historical data access (HDA) through an abstract IHistorianDataSource interface (Historian/IHistorianDataSource.cs). The Wonderware Historian implementation lives in a separate assembly, ZB.MOM.WW.LmxOpcUa.Historian.Aveva, which is loaded at runtime only when Historian.Enabled=true. This keeps the aahClientManaged SDK out of the core Host so deployments that do not need history do not need the SDK installed.

Plugin Architecture

The historian surface is split across two assemblies:

• ZB.MOM.WW.LmxOpcUa.Host (core) owns only OPC UA / BCL types:
  • IHistorianDataSource -- the interface LmxNodeManager depends on
  • HistorianEventDto -- SDK-free representation of a historian event record
  • HistorianAggregateMap -- maps OPC UA aggregate NodeIds to AnalogSummary column names
  • HistorianPluginLoader -- loads the plugin via Assembly.LoadFrom at startup
  • HistoryContinuationPointManager -- paginates HistoryRead results
• ZB.MOM.WW.LmxOpcUa.Historian.Aveva (plugin) owns everything SDK-bound:
  • HistorianDataSource -- implements IHistorianDataSource, wraps aahClientManaged
  • IHistorianConnectionFactory / SdkHistorianConnectionFactory -- opens and polls ArchestrA.HistorianAccess connections
  • AvevaHistorianPluginEntry.Create(HistorianConfiguration) -- the static factory invoked by the loader

The plugin assembly and its SDK dependencies (aahClientManaged.dll, aahClient.dll, aahClientCommon.dll, Historian.CBE.dll, Historian.DPAPI.dll, ArchestrA.CloudHistorian.Contract.dll) deploy to a Historian/ subfolder next to ZB.MOM.WW.LmxOpcUa.Host.exe. See Service Hosting for the full layout and deployment matrix.

Plugin Loading

When the service starts with Historian.Enabled=true, OpcUaService calls HistorianPluginLoader.TryLoad(config). The loader:

1. Probes AppDomain.CurrentDomain.BaseDirectory\Historian\ZB.MOM.WW.LmxOpcUa.Historian.Aveva.dll.
2. Installs a one-shot AppDomain.AssemblyResolve handler that redirects any aahClientManaged/aahClientCommon/Historian.* lookups to the same subfolder, so the CLR can resolve SDK dependencies when the plugin first JITs.
3. Calls the plugin's AvevaHistorianPluginEntry.Create(HistorianConfiguration) via reflection and returns the resulting IHistorianDataSource.
4. On any failure (plugin missing, entry type not found, SDK assembly unresolvable, bad image), logs a warning with the expected plugin path and returns null. The server starts normally and LmxNodeManager returns BadHistoryOperationUnsupported for every history call.

Wonderware Historian SDK

The plugin uses the AVEVA Historian managed SDK (aahClientManaged.dll) to query historical data. The SDK provides a cursor-based query API through ArchestrA.HistorianAccess, replacing direct SQL queries against the Historian Runtime database. Two query types are used:

• HistoryQuery -- Raw historical samples with timestamp, value (numeric or string), and OPC quality.
• AnalogSummaryQuery -- Pre-computed aggregates with properties for Average, Minimum, Maximum, ValueCount, First, Last, StdDev, and more.

The SDK DLLs are located in lib/ and originate from C:\Program Files (x86)\Wonderware\Historian\. Only the plugin project (src/ZB.MOM.WW.LmxOpcUa.Historian.Aveva/) references them at build time; the core Host project does not.

Configuration

HistorianConfiguration controls the SDK connection:

public class HistorianConfiguration
{
    public bool Enabled { get; set; } = false;
    public string ServerName { get; set; } = "localhost";
    public bool IntegratedSecurity { get; set; } = true;
    public string? UserName { get; set; }
    public string? Password { get; set; }
    public int Port { get; set; } = 32568;
    public int CommandTimeoutSeconds { get; set; } = 30;
    public int MaxValuesPerRead { get; set; } = 10000;
}

When Enabled is false, HistorianPluginLoader.TryLoad is not called, no plugin is loaded, and the node manager returns BadHistoryOperationUnsupported for history read requests. When Enabled is true but the plugin cannot be loaded (missing Historian/ subfolder, SDK assembly resolve failure, etc.), the server still starts and returns the same BadHistoryOperationUnsupported status with a warning in the log.

Connection Properties

Property	Default	Description
ServerName	localhost	Historian server hostname
IntegratedSecurity	true	Use Windows authentication
UserName	null	Username when IntegratedSecurity is false
Password	null	Password when IntegratedSecurity is false
Port	32568	Historian TCP port
CommandTimeoutSeconds	30	SDK packet timeout in seconds
MaxValuesPerRead	10000	Maximum values per history read request

Connection Lifecycle

HistorianDataSource (in the plugin assembly) maintains a persistent connection to the Historian server via ArchestrA.HistorianAccess:

1. Lazy connect -- The connection is established on the first query via EnsureConnected().
2. Connection reuse -- Subsequent queries reuse the same connection.
3. Auto-reconnect -- On connection failure, the connection is disposed and re-established on the next query.
4. Clean shutdown -- Dispose() closes the connection when the service stops.

The connection is opened with ReadOnly = true and ConnectionType = Process.

Raw Reads

IHistorianDataSource.ReadRawAsync (plugin implementation) uses a HistoryQuery to retrieve individual samples within a time range:

1. Create a HistoryQuery via _connection.CreateHistoryQuery()
2. Configure HistoryQueryArgs with TagNames, StartDateTime, EndDateTime, and RetrievalMode = Full
3. Iterate: StartQuery -> MoveNext loop -> EndQuery

Each result row is converted to an OPC UA DataValue:

• QueryResult.Value (double) takes priority; QueryResult.StringValue is used as fallback for string-typed tags.
• SourceTimestamp and ServerTimestamp are both set to QueryResult.StartDateTime.
• StatusCode is mapped from the QueryResult.OpcQuality (UInt16) via QualityMapper (the same OPC DA quality byte mapping used for live MXAccess data).

Aggregate Reads

IHistorianDataSource.ReadAggregateAsync (plugin implementation) uses an AnalogSummaryQuery to retrieve pre-computed aggregates:

1. Create an AnalogSummaryQuery via _connection.CreateAnalogSummaryQuery()
2. Configure AnalogSummaryQueryArgs with TagNames, StartDateTime, EndDateTime, and Resolution (milliseconds)
3. Iterate the same StartQuery -> MoveNext -> EndQuery pattern
4. Extract the requested aggregate from named properties on AnalogSummaryQueryResult

Null aggregate values return BadNoData status rather than Good with a null variant.

Quality Mapping

The Historian SDK returns standard OPC DA quality values in QueryResult.OpcQuality (UInt16). The low byte is passed through the shared QualityMapper pipeline (MapFromMxAccessQuality -> MapToOpcUaStatusCode), which maps the OPC DA quality families to OPC UA status codes:

OPC Quality Byte	OPC DA Family	OPC UA StatusCode
0-63	Bad	Bad (with sub-code when an exact enum match exists)
64-191	Uncertain	Uncertain (with sub-code when an exact enum match exists)
192+	Good	Good (with sub-code when an exact enum match exists)

See Domain/QualityMapper.cs and Domain/Quality.cs for the full mapping table and sub-code definitions.

Aggregate Function Mapping

HistorianAggregateMap.MapAggregateToColumn (in the core Host assembly, so the node manager can validate aggregate support without requiring the plugin to be loaded) translates OPC UA aggregate NodeIds to AnalogSummaryQueryResult property names:

OPC UA Aggregate	Result Property
AggregateFunction_Average	Average
AggregateFunction_Minimum	Minimum
AggregateFunction_Maximum	Maximum
AggregateFunction_Count	ValueCount
AggregateFunction_Start	First
AggregateFunction_End	Last
AggregateFunction_StandardDeviationPopulation	StdDev

Unsupported aggregates return null, which causes the node manager to return BadAggregateNotSupported.

HistoryReadRawModified Override

LmxNodeManager overrides HistoryReadRawModified to handle raw history read requests:

1. Resolve the NodeHandle to a tag reference via _nodeIdToTagReference. Return BadNodeIdUnknown if not found.
2. Check that _historianDataSource is not null. Return BadHistoryOperationUnsupported if historian is disabled.
3. Call ReadRawAsync with the time range and NumValuesPerNode from the ReadRawModifiedDetails.
4. Pack the resulting DataValue list into a HistoryData object and wrap it in an ExtensionObject for the HistoryReadResult.

HistoryReadProcessed Override

HistoryReadProcessed handles aggregate history requests with additional validation:

1. Resolve the node and check historian availability (same as raw).
2. Validate that AggregateType is present in the ReadProcessedDetails. Return BadAggregateListMismatch if empty.
3. Map the requested aggregate to a result property via MapAggregateToColumn. Return BadAggregateNotSupported if unmapped.
4. Call ReadAggregateAsync with the time range, ProcessingInterval, and property name.
5. Return results in the same HistoryData / ExtensionObject format.

Historizing Flag and AccessLevel

During variable node creation in CreateAttributeVariable, attributes with IsHistorized == true receive two additional settings:

if (attr.IsHistorized)
    accessLevel |= AccessLevels.HistoryRead;
variable.Historizing = attr.IsHistorized;

• Historizing = true -- Tells OPC UA clients that this node has historical data available.
• AccessLevels.HistoryRead -- Enables the HistoryRead access bit on the node, which the OPC UA stack checks before routing history requests to the node manager override. Nodes without this bit set will be rejected by the framework before reaching HistoryReadRawModified or HistoryReadProcessed.

The IsHistorized flag originates from the Galaxy repository database query, which checks whether the attribute has Historian logging configured.