OPC COM Call Tracing

Overview

OPC COM Call Tracing is a built-in software component that records OPC COM method calls made on your OPC server.

OPC COM Call Tracing is implemented by the NDI TraceHook Component, a DLL that hooks into OPC COM calls to capture and record the call stack. Call stack information is decoded, annotated, and logged to a circular file. Refer to the diagram.

Since the TraceHook component hooks the COM calls (and does not operate in a pass-through mode) OPC COM Call Tracing is very efficient, imposing very little run-time overhead. Therefore, timing related integration problems can be diagnosed.

The TraceHook component ships with a simple utility application that allows tracing parameters to be changed dynamically.

Details

OPC COM Call Tracing logs timestamped, thread-specific details for all OPC DA interface method calls. Developers use this tool to create an exhaustive and annotated audit trail of OPC interface calls on your server. When activated, the following information is logged for each OPC interface call. Click here to view a sample log file.

Pre- or Post-method call timestamp.

Unique COM object ID for identifying the object instance making the call.

Unique, sequential call ID for identifying the order of calls on a per thread basis.

Interface name and method name.

HRESULT for post-call messages.

[in] and [out] parameter values.

The following levels of COM call details can be selected for logging.

Only failed method calls.

All method calls with HRESULTs only.

Pre- and post- method call trace messages to calculate call timing.

Pre- and post- method call trace messages with full [in] and [out] parameter dump.

For all levels, a filter expression can be specified. You can dynamically filter the message stream, reducing the amount of information logged to that which is of interest.

Demo OPC COM Call Tracing

OPC COM Call Tracing has been included with the simulation server (installed with the OPC DA Server Toolkit demo software). Just enable the COM Call Tracing option and connect to the simulation server using your OPC client.