Editing Distributed control system (section)

===The application-centric era of the 1990s===
The drive toward openness in the 1980s gained momentum through the 1990s with the increased adoption of [[commercial off-the-shelf]] (COTS) components and IT standards.  Probably the biggest transition undertaken during this time was the move from the UNIX operating system to the Windows environment.  While the realm of the real time operating system ([[RTOS]]) for control applications remains dominated by real time commercial variants of UNIX or proprietary operating systems, everything above real-time control has made the transition to Windows.

The introduction of Microsoft at the desktop and server layers resulted in the development of technologies such as [[OLE for process control|OLE for process control (OPC)]], which is now a de facto industry connectivity standard.  Internet technology also began to make its mark in automation and the  world, with most DCS HMI supporting Internet connectivity.  The 1990s were also known for the "Fieldbus Wars", where rival organizations competed to define what would become the IEC [[fieldbus]] standard for digital communication with field instrumentation instead of 4–20 milliamp analog communications.  The first fieldbus installations occurred in the 1990s.  Towards the end of the decade, the technology began to develop significant momentum, with the market consolidated around Ethernet I/P, Foundation Fieldbus and Profibus PA for process automation applications.  Some suppliers built new systems from the ground up to maximize functionality with fieldbus, such as [[Rockwell Automation|Rockwell]] PlantPAx System, [[Honeywell]] with [[Experion]] & Plantscape [[SCADA]] systems, [[ABB]] with System 800xA,<ref>{{cite web|url=http://www.abb.com/product/us/9AAC115756.aspx|title=ABB System 800xA - process, electrical, safety, telecoms in one system|website=www.abb.com}}</ref> Emerson Process Management<ref>[http://easydeltav.com] [[Emerson Process Management]]</ref> with the [[Emerson Process Management]] [[DeltaV]] control system, [[Siemens]] with the SPPA-T3000<ref>[http://www.energy.siemens.com/hq/en/automation/power-generation/sppa-t3000.htm] {{Webarchive|url=https://web.archive.org/web/20180203212221/https://www.energy.siemens.com/hq/en/automation/power-generation/sppa-t3000.htm|date=2018-02-03}} SPPA-T3000</ref> or [[Simatic PCS 7]],<ref>{{cite web |url=http://pcs.khe.siemens.com/index.aspx?nr%3D1075 |title=Siemens - SIMATIC PCS 7 - SIMATIC PCS 7 (SIMATIC, PCS 7, process control system, SIMATIC PCS7, Add Ons, solutions for industry, process automation, process industry) |access-date=2007-03-29 |url-status=dead |archive-url=https://web.archive.org/web/20070329065215/http://pcs.khe.siemens.com/index.aspx?nr=1075 |archive-date=2007-03-29 }} Simatic PCS 7</ref> Forbes Marshall<ref>[http://www.forbesmarshall.com/fm_micro/DCS/Products1.aspx?flag=1&id=dcs&pid=551&prodName=Microcon+%20Distributed%20Control%20System(DCS)] [[Forbes Marshall]]</ref> with the Microcon+ control system and {{Ill|Azbil|lt=Azbil Corporation|ja|アズビル}}<ref>[http://www.azbil.com] Azbil Corporation</ref> with the [[Harmonas-DEO]] system. Fieldbus technics have been used to integrate machine, drives, quality and [[condition monitoring]] applications to one DCS with Valmet DNA system.<ref name="Valmet" />

The impact of COTS, however, was most pronounced at the hardware layer.  For years, the primary business of DCS suppliers had been the supply of large amounts of hardware, particularly I/O and controllers.  The initial proliferation of DCSs required the installation of prodigious amounts of this hardware, most of it manufactured from the bottom up by DCS suppliers.  Standard computer components from manufacturers such as Intel and Motorola, however, made it cost prohibitive for DCS suppliers to continue making their own components, workstations, and networking hardware.

As the suppliers made the transition to COTS components, they also discovered that the hardware market was shrinking fast.  COTS not only resulted in lower manufacturing costs for the supplier, but also steadily decreasing prices for the end users, who were also becoming increasingly vocal over what they perceived to be unduly high hardware costs. Some suppliers that were previously stronger in the [[programmable logic controller|PLC]] business, such as Rockwell Automation and Siemens, were able to leverage their expertise in manufacturing control hardware to enter the DCS marketplace with cost effective offerings, while the stability/scalability/reliability and functionality of these emerging systems are still improving. The traditional DCS suppliers introduced new generation DCS System based on the latest Communication and IEC Standards, which resulting in a trend of combining the traditional concepts/functionalities for PLC and DCS into a one for all solution—named "[[Process Automation System]]" (PAS). The gaps among the various systems remain at the areas such as: the database integrity, pre-engineering functionality, system maturity, communication transparency and reliability. While it is expected the cost ratio is relatively the same (the more powerful the systems are, the more expensive they will be), the reality of the automation business is often operating strategically case by case. The current next evolution step is called [[Collaborative Process Automation Systems]].

To compound the issue, suppliers were also realizing that the hardware market was becoming saturated.  The life cycle of hardware components such as I/O and wiring is also typically in the range of 15 to over 20 years, making for a challenging replacement market.  Many of the older systems that were installed in the 1970s and 1980s are still in use today, and there is a considerable installed base of systems in the market that are approaching the end of their useful life.  Developed industrial economies in North America, Europe, and Japan already had many thousands of DCSs installed, and with few if any new plants being built, the market for new hardware was shifting rapidly to smaller, albeit faster growing regions such as China, Latin America, and Eastern Europe.

Because of the shrinking hardware business, suppliers began to make the challenging transition from a hardware-based business model to one based on software and value-added services.  It is a transition that is still being made today.  The applications portfolio offered by suppliers expanded considerably in the '90s to include areas such as production management, model-based control, real-time optimization, plant asset management (PAM), Real-time performance management (RPM) tools, [[alarm management]], and many others.  To obtain the true value from these applications, however, often requires a considerable service content, which the suppliers also provide.