Limitations

Table of Contents

• Mapping of COM Variant Data Types to OPC UA Data Types
• Mapping of COM DA Properties to OPC UA
• COM HDA Aggregates
• No Remote DCOM Connections
• No Multiple UaGateway Installations

Mapping of COM Variant Data Types to OPC UA Data Types

When mapping the address space of an underlying COM DA server to the address space of UaGateway’s OPC UA server, COM Variant data types are converted to OPC UA data types. Currently, the following conversions are supported:

Variant Type	OPC UA Type
VT_EMPTY	NULL
VT_BOOL	Boolean
VT_I1	SByte
VT_I2	Int16
VT_I4	Int32
VT_I8	Int64
VT_UI1	Byte
VT_UI2	UInt16
VT_UI4	UInt32
VT_UI8	UInt64
VT_R4	Float
VT_R8	Double
VT_CY	Double (possible out of range conversion error)
VT_BSTR	String
VT_DATE	DateTime

Mapping of COM DA Properties to OPC UA

For underlying COM DA servers, only the standard properties (AttributeID 1-6, value, timestamp, quality) are mapped to OPC UA. All other COM DA properties are not mapped but ignored.

Note that OPC UA Properties of an underlying OPC UA Server can be mapped to vendor-specific attributes (see Property mapping from UA to COM DA).

COM HDA Aggregates

Aggregates of underlying COM HDA Servers are not made available via UaGateway’s OPC UA Server, only raw historical data.

No Remote DCOM Connections

UaGateway runs as a Windows service and thus in a service context with dedicated user rights, which means that remote DCOM connections are not possible. Thus, the UaGateway always has to run on the same machine as the COM DA Clients/Servers that should be connected.

No Multiple UaGateway Installations

It is only possible to install a single UaGateway on the same PC, multiple installations are not possible. This has to be especially kept in mind when installing an OEM Edition of UaGateway, which can’t be run side by side with a “regular” UaGateway.