OPC or Database: How are People Connecting?

In connecting plant data to the business side, companies are turning to recently developed standards that can make the arc from the shop floor to the business side. “You can do it a couple different ways,” explains James David, senior applications engineer at vendor Opto 22, in Temecula, Calif. “You can drive it through a database to a Microsoft SQL Server, or you can use a direct connection through OPC.”

OPC (an open connectivity standard) has been getting a lot of attention in the field of connecting the plant to business systems, especially the most recent OPC UA (Unified Architecture), which was released to the OPC membership last fall. The strategy behind OPC UA, according to analyst firm ARC Advisory Group Inc., in Dedham, Mass., is to leverage collaboration with other industry standards, including ISA-S95, ISA-S99, OAGi, EDDL and MIMOSA. The OPC UA is intended to focus on how to move data from these other standards organizations and define the “semantics of content.”

Craig Resnick, research director at ARC, notes that “the foundation of OPC UA includes all of the necessary services to provide secure, reliable interoperability across platforms, leveraging Web Services and the collaborative effort with other industry standards organizations.” He notes that newly developed parts of OPC UA specialize in services required for alarms and events, data exchange and historical data access.

Opto 22’s David also notes that connectivity can be made between the plant and business systems without using OPC. “Without OPC, the controller data can go right to a database, and the database can be accessed through the ERP (enterprise resourse planning) system or MES (manufacturing execution system). However you do it, once you get the data into SQL, you’re golden.”

A recent survey by AMR Research Inc., in Boston, shows that the majority of plants are using ISA-S95 as the primary standard for exchanging plant data with ERP systems. A hearty 59 percent use ISA-S95. Another 25 percent are using ISA-S88, while 22 percent are using OAGi (a communication standard from the Open Applications Group) and 15 percent are using any number of other standards.

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