White Papers

In-depth discussions of DataHub technology

Networking OPC is challenging because it relies on DCOM. The most practical way to network OPC is to avoid DCOM and tunnel OPC. This paper explains the problems with DCOM, and why tunnelling OPC provides a more reliable, secure, and easy-to-use approach. It also covers advanced tunnelling topics such as reducing bandwidth, non-blocking tunnels, slow networks, and more. Read more…

There are a number of tunnelling products on the market. How can you know which one is best? This paper gives a clear explanation of the major approaches to tunnelling OPC, how each approach handles network issues and supports multiple connections, and what to look for regarding security. Read more…

Many OPC-based systems require high availability of source data. This is often achieved through redundancy. This paper discusses the major concepts for redundant systems, such as hot/warm/cold standby, switchovers and fallbacks, the timer pitfall, object and link monitoring, preferred sources, and others. Read more…

There are a number of ways that the Cogent DataHub can be used to implement redundancy in an OPC-based system. This document illustrates a few of the most common scenarios. Read more…

In the automation and process control world, there are two important ways to archive data: logging it to a database or feeding it to a real-time historian. Although a relational database has many advantages, this paper gives three reasons why that approach may not be sufficient. Read more…

Every once in a while we get asked: “Can I store and forward my OPC data?” A little understanding of the purpose of OPC, and how it works, should make it clear that the answer to this question is effectively “No ‘not when it comes to real-time data, anyway.” Read more…