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Historians Bring Relief to Data Explosion

Regardless of whose control technology they have, end-users need help in correctly and securely gathering, storing and retrieving data.

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That’s more essential than ever today, because the quantity of information to be gathered and stored is “exploding,” observes Pat Kennedy, president and chief executive officer of software vendor OSIsoft Inc. (, San Leandro, Calif.

Once, though, data were discarded because there was no other choice, he recalls. That’s changed through scale-out in systems, which can be devised so “you can scale by just adding more and more processors,” Kennedy explains. Historically, the problem wasn’t the processors, he adds, but “the software to manage those processors and give a unified view to the people who needed it.”

Along the way to expanded data collection and storage, however, confusion has arisen about software historians—which provide long-term data storage and retrieval—vs. trending packages and data logging, which usually find use with specific applications. “Control systems forever have had the trending package,” says Kennedy, providing access to collected data for intervals of hours or days. “[But] since you’re addressing current needs of an operator, it tends to have high-fidelity information [only] for a while, then shifts to trends,” he explains.

Historians preserve the fidelity—reliability or trustworthiness—of information. They do so by accurately warehousing gathered data sent to them until retrieval later for whatever purpose end-users might have. And they facilitate quick recovery of those data. “A historian doesn’t know why people are after data,” Kennedy notes. “Historians tend to keep all the data, in all their fidelity, for as long as they can.”

That can improve companies’ operational flexibility, and thus performance. “Store enough data so that there is no need to gather [more] data as part of improving the process,” Kennedy advises. “This shortens the [improvement] cycle, and creates agility and flexibility.” Citing control valves as an example, he says, “Once you go to a digital control valve, there could be 150 [data] points that could be stored.” Even if there were thousands of machines with thousands of points, he suggests that with a historian, “you could store them [the data] to a centralized system.” And that will allow not just initial aggregation of those data, but the ability later to drill down into them.

That data mining could continue indefinitely. “Realistically, we monitor the events that come out of a facility and we store them—the data—forever,” Kennedy explains about PI System, his company’s enterprise-oriented historian. Unlike traditional historians, this type of historian helps connect the plant floor to the rest of the business by not only gathering and archiving data, but also processing them.

Processing data

Nearly a year ago, OSIsoft and vendor Rockwell Automation Inc. (, Milwaukee, entered an agreement to take OSIsoft’s historian technology and build it on top of FactoryTalk, Rockwell’s service-oriented architecture. “That means it (the historian) has things such as data access, auditing, diagnostics and security,” notes Kevin Roach, Rockwell Software vice president.

The alliance plans three products. Site Edition, which targets supervisory-level monitoring-and-control applications and which Kennedy calls a rebranded Microsoft Corp. ( Windows-based PI System, appeared in June. Machine Edition, built into Rockwell’s integrated architecture through ControlLogix, will be another product, Roach says. It’s a “a full-bore historian, not a data collector meant just to talk to something else,” Kennedy adds. The third product is Enterprise Edition. Though it will carry OSIsoft’s name, Rockwell will market and distribute it, Kennedy explains. “It will allow aggregation of multiple Site Edition servers.” That aggregation sounds like what a historian would do.

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