A manufacturing execution system, or MES, is the software layer that manages and tracks production as it actually happens on the plant floor. It sits between the control systems below and the enterprise planning systems above, turning a high-level production plan into executed, documented work. In the ISA-95 model, MES lives at Level 3 - the operations layer between SCADA and ERP.
MES in one line: A manufacturing execution system (MES) is software that manages, monitors, and documents production on the plant floor - scheduling work, tracking materials and product genealogy, and enforcing quality - bridging control systems below and enterprise ERP above, at ISA-95 Level 3.
An MES coordinates the execution of production. Typical functions include detailed scheduling and dispatching of work orders, tracking materials and product genealogy (what went into each unit and where it came from), collecting production and quality data, managing work instructions, and reporting performance metrics like yield and downtime. It answers the operational questions ERP cannot: what is being made right now, on which line, with which materials, and to what quality.
The MES draws real-time data from the control layer - PLC, DCS, and SCADA - and hands finished production and inventory results up to ERP. This makes it the translation layer between the fast, physical world of the plant floor and the slower, financial world of the enterprise. In heavily regulated industries, the MES is also where electronic batch records and compliance documentation are captured.
MES is easy to confuse with SCADA and ERP, but each has a distinct job. SCADA monitors and controls equipment in real time. ERP plans the business - orders, procurement, finance - over days and weeks. MES fills the gap between them, managing the execution of production shift by shift. SCADA data feeds the MES; MES results feed the ERP.
MES is fundamentally a discrete- and batch-manufacturing concept - think automotive, pharmaceuticals, food and beverage. In oil and gas, classic MES is less common; upstream and midstream operations lean on SCADA, production accounting, and hydrocarbon allocation systems that play a similar Level 3 role without always carrying the MES label. Where a Level 3 system needs live field data, a cloud SCADA platform like Merobix can supply it through APIs after reading devices over Modbus, OPC UA, and other protocols.
SCADA monitors and controls equipment in real time at the supervisory level; MES manages and documents production execution - scheduling, material tracking, and quality - one layer above. SCADA data typically feeds into the MES, which then reports results up to ERP.
ERP plans and runs the business - orders, finance, procurement - over days and weeks, while MES executes and tracks production on the plant floor in real time. MES sits between the control layer and ERP, translating between physical operations and business systems.
Classic MES is more common in discrete and batch manufacturing. Oil and gas operations often use SCADA together with production accounting and hydrocarbon allocation systems to fill the equivalent Level 3 role, rather than a system branded as MES.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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