OPC DA Client

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Product Overview

OPC DA stands for OPC Data Access. OPC Data Access (OPC DA) provides access to real time automation data. Using OPC DA, software applications can retrieve real-time data to enable them to monitor a given process.

The OPC DA Client driver and Kepware communications platform provide an easy and reliable way to connect disparate third-party OPC DA servers to your client applications, including HMI, SCADA, Historian, MES, ERP, and countless custom applications.

With the OPC DA Client driver you can manage operations through a single server interface, so there is no need to learn the different nuances of other third-party servers.

This driver also enables Oracle MES and MOC users to bring Kepware OPC operations and all other third-party OPC operations into your business applications.

  • Provides a single, reliable connection point to access data from multiple OPC servers on local and remote machines
  • Enables optimized performance of OPC servers through OPC groupings that may be different than those required or allowed by your clients
  • Supports connection monitoring and reconnect behavior for each OPC server
  • Provides connectivity to remote OPC servers for clients that do not support DCOM
  • Allows connectivity to multiple OPC servers from clients that do not support multiple connections or handle multiple connections well
  • Allows connectivity to OPC servers using different interfaces that are supported by clients, such as DDE, Wonderware SuiteLink, GE NIO, and so forth
  • Supports update by exception (Watchdog)
  • Automatically import OPC Server Items
  • OPC Data Access (DA)
  • OPC DA Servers: 1.0, 2.0, and 3.0
  • English
  • DDE Format CF_Text and AdvancedDDE
  • NIO Interface for iFIX
  • OPC .NET Service (OPC .NET) Version 1.00
  • OPC Alarms and Events (OPC AE) Version 1.10
  • OPC Data Access (OPC DA) Versions 1.0a, 2.0, 2.05a, and 3.0
  • OPC Unified Architecture (OPC UA) Clients
  • SuiteLink and FastDDE for Wonderware



  • Fixed an issue with browsing for and importing tags with special characters (e.g. O₂).



  • Fixed an issue where item adds were rejected after a server restart.



  • Fixed an issue that prevented successful DA 3.0 writes.
  • Fixed an issue when trying to write to tags before they are added to a subscription.
  • The driver rebuilds the connection if the device level group fails to add, similar to a shutdown notification, status, or watchdog failure.



  • Added a runtime system tag (_OPCGroupActive) that allows the user to set the OPCGroup to active/inactive, helpful when working with older OPC servers.
  • Fixed an issue where use of the SimpleItemIO::WriteVQT interface would cause a CPU spike if the intended target device of the write was offline.



  • Resolved a memory leak.
  • Fixed an issue where the driver would fail to read/write if callbacks failed even if the driver was configured for synchronous reads and writes.


  • Improved performance when collapsing/expanding/importing items using the Browse Import Items dialog.
  • Fixed an issue where consecutive writes of the same value could result in bad tag quality.



  • UI import items performance improvements.
  • Added an enable/disable box to controls whether an explicit read occurs after a write.



  • Fixed a crash issue when loading a project with an OPC DA Client using OPC DA 1.0.



  • Added an enable/disable box to control whether an explicit read occurs after a write.



  • Fixed an issue where both the client and server were deleting the same memory in 1.0.



  • Fixed issue where removing invalid items could result in a runtime failure.


  • Added OPC DA 3.0 support.


  • Enhanced the driver to support DA 3.0 browsing.
  • Resolved an issue where removing invalid items could result in a hang of the runtime.


  • Refactored how the driver re-adds failed items. When items were continuously added and removed by the client where at least one of the items was invalid, it could lead to “Bad” quality of valid items and instability of the runtime.



  • Enabled 64-bit data type support (LLong, QWord).
  • Added support for OPC Item Access Path using $ symbol for delimiters.
  • Enhanced the driver to allow OPC DA Read and Write methods (Asynchronous or Synchronous) based on the Update Mode of the OPC Group. Asynchronous Read and Write methods are the default and remain the optimal choice for most applications.



  • Enhanced Automatic Tag Generation for a device object while one or more clients are actively connected.
  • Resolved an issue that could cause tag reads using ReadMaxAge to always read from cache.
  • Resolved an issue that could cause the client to receive a newly written value, then a stale cached value, before receiving the new value again. 



  • Enhanced the OPC DA Client Driver so that it will now attempt to re-add failed items.



  • Fixed an issue where the server could crash if an In-Process Server (which is a server that is a .dll not an .exe) threw an unhandled exception.



  • Fixed an issue where AddGroup() calls would fail when CoInitializeEx () was called after CoInitializeSecurity ().


  • Resolved an issue where the driver would invalidate tags if the remote server did not provide a supported data type when the item was added to the server. The driver will now wait for the first update before invalidating unsupported data types.



  • Previously, the driver would automatically filter out the data types that it could not resolve in a browser. It will now import these tags using the Default data type, and will also post a message to the Event Log.
  • Fixed an exception that would occur when invalidating tags while unloading the driver.
  • Fixed a reconnect issue where the shutdown sink flag was not cleared.
  • Fixed an issue where valid data change events were thrown away because the driver received data change events on items before they were fully added.



  • Fixed an issue in the Tag Import Browser where parent node tags would be imported even when only a child node was selected.


  • Changed the default update rate from 50 milliseconds to 1000 milliseconds.


  • Improved initial update performance when there is a mix of good and non-good data items from the underlying servers.


  • Added support for two-dimensional arrays.


  • When adding groups, the time bias is now properly initialized to zero. At this moment, this setting is not user-configurable.
  • Fixed an issue wherein the initial update was not passed on to client applications.
  • Removed the limit that prevented the creation of nested groups with depth greater than 8.


  • The driver now reports a value, quality, and timestamp for invalid tags (tags that can't be added to the remote server). Previously we would keep attempting to read the tags, expecting an initial update. In the case that the tag is invalid, we won't receive an update, and should report the tag is Bad: Out of Service.
  • Improved performance of ATG.
  • The driver now removes all items from the underlying server when the DA Client's device is configured as disabled.
  • Fixed issue where the driver returned an invalid read value when an item did not receive an update from the DA Server. We now continue to process the read request until we have a valid return value.