OPC evolution toward Unix

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OPC evolution toward Unix
From Windows to World Wide Domination?

• Communication standards within a DCS
• OPC Data Access
• OPC on Unix
• The future

• Mark Beharrell IT/CO, CERN, Geneva, Switzerland
  ICALEPCS ? October 12th, 2005

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

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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

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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

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Why OPC on Unix

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

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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?

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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

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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

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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.

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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

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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.

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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!