Level 4

In the ISA-95 reference model, Level 4 refers to the business-planning and logistics layer that manages how the enterprise plans, schedules, and analyzes production, but does not directly control equipment on the shop floor.

What Level 4 includes

Level 4 commonly covers systems and functions such as:

• Enterprise Resource Planning (ERP) for order management, material planning, and financial posting related to production
• Advanced Planning & Scheduling (APS) and production planning tools
• Sales & Operations Planning (S&OP) and demand planning processes
• Logistics and inventory management at the enterprise level
• Business performance reporting and analytics for production, cost, and capacity

These systems determine what should be produced, when, and in which quantities, based on demand, capacity, and business objectives. They exchange information with Level 3 manufacturing operations systems but are typically not responsible for real-time control.

What Level 4 does not include

In ISA-95, Level 4 does not include:

• Detailed dispatching of work to specific machines or operators (Level 3 activity)
• Supervisory control and data acquisition, control logic, or interlocks (Levels 1 and 2)
• Physical sensors, actuators, and field devices (Level 0)

Some organizations use hybrid tools that span Level 3 and Level 4 capabilities, but ISA-95 uses Level 4 to describe the business-planning perspective rather than real-time execution.

Operational context in manufacturing

Operationally, Level 4 systems:

• Send planned production orders, material requirements, and schedules down to Level 3 systems (such as MES)
• Receive actual production data, material consumption, and quality summaries back from Level 3
• Support decision making on capacity, sourcing, and long- to medium-term planning

This separation allows plants to model interfaces between enterprise IT and manufacturing operations in a consistent way across sites and systems.

Common confusion

• Level 4 vs. Level 3: Level 3 focuses on manufacturing operations management (e.g., MES, detailed scheduling, dispatching, track & trace), while Level 4 focuses on enterprise and business-planning functions (e.g., ERP, APS). Level 4 plans and analyzes; Level 3 executes and coordinates on the shop floor.
• Level 4 vs. network layers: In some IT and OT networking contexts, “Layer 4” can refer to the transport layer in the OSI model. ISA-95 Level 4 is unrelated to networking layers and instead describes a functional level of business systems.

Relation to ISA-95

Within ISA-95, Level 4 is one of the defined functional levels used to describe how business systems integrate with manufacturing operations. The standard uses Level 4 to classify functions, data flows, and interfaces at the enterprise planning and logistics level, helping structure integration between ERP and manufacturing systems without prescribing specific products or architectures.