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Evolution of OPC: From Windows to World Wide Domination?

Explore the transition of OPC from Windows to Unix, comparing DCOM and OPC XML DA, and the introduction of OPC Unified Architecture in 2005. Discusses performance and stability tests on Linux platforms.

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Evolution of OPC: From Windows to World Wide Domination?

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  1. OPC evolution toward Unix From Windows to World Wide Domination? Mark Beharrell IT/CO, CERN, Geneva, SwitzerlandICALEPCS ― October 12th, 2005 • Communication standards within a DCS • OPC Data Access • OPC on Unix • The future

  2. Data Flows within a Detector Control System DCS Accelerator Web Access Supervisor (SCADA) Experiment General Services Devices Safety

  3. Device communication • Device access protocols vary between:- • Manufacturers • Models • Versions of models • Want an ‘interpreter’ • Hide device differences • Developed by 3rd party • What protocol to use with the interpreter?

  4. Middleware • General solutions • CORBA • Java RMI • DCOM • General solutions are not sufficient • Must solve a specific problem in standard way • Need Standardize to level of the device • “Data Acquisition” • “OPC Data Access”

  5. The OPC DA solution • 1996 - OPC Data Access 1.0 • Well defined specification giving • Device model • Data model • Communications model • Acceptance • Wide user base • Uses DCOM middleware

  6. Why OPC on Unix • Motivation • Single protocol for all device oriented • communications • Possibilities • DCOM on Linux • OPC XML DA • OPC Unified Architecture

  7. 1. DCOM on Linux • 1996 – Microsoft release the DCOM Spec. • Implementations on Solaris, VxWorks, Linux • DCOM → OPC • OPC DA (DCOM) Servers on Linux • Performance? • Stability?

  8. 1. DCOM-Performance & stability • Test • Windows OPC server ported to Linux • Measured time to read OPC items (float) on both platforms • Result • Windows OPC ~ 100,000 items per second • Linux OPC ~ 76,000 items per second • Problems • OPC server itself was stable • ‘System issues’

  9. 2. OPC XML DA • 2003 – OPC XML DA released • Similar to the DA specification • Same device and data model • Different communication model • Based on Web Services • OPC XML DA on any TCP/IP enabled processor

  10. 2. XML-Performance & stability • Test • Wrote OPC XML server using toolkit. • Measured time to read OPC items (float) on both platforms • Result • OPC XML DA ~ 6,000 items per second • Verses 76,000 with OPC on Linux! • Problems • ~5 items per second for single OPC item reads! • Interface definition does not always translate to code correctly.

  11. 3. OPC Unified Architecture • 2005 – OPC UA introduced • But not yet released • Fusion of OPC interfaces • “Integration of plant floor data into enterprise systems and the internet” • Provide secure, reliable and efficient services • Protocol and platform independence • DCOM to be ‘retired’ • Replaced by SOAP based alternatives

  12. Low industrial acceptance Not yet available It works but is it useful? • Several solutions to OPC servers on Unix. • DCOM based • OPC XML DA • OPC UA • Waste of time ? - NO • OPC DA clients on Linux based SCADA systems.

  13. Internet Enterprise Factory Platforms Into the future • OPC DA lives for the time being • OPC XML will be replaced by UA • OPC UA holds promise. • But World Wide Domination? For device access – maybe!

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