Untitled

Architecture and System Hierarchy

A warehouse execution system maintains continuous synchronization between digital records and physical material movements. Belimo divides this domain across four specialized architectural layers, preventing any single application from bearing the entire operational and business burden.

The Four-Layer Architectural Model

The warehouse execution stack comprises four functional layers:

SAP (ERP / Inventory Master): Serves as the ultimate system of record and master system for inventory quantities, material master data, plant structures, purchasing, customer orders, production orders, and overall warehouse strategies. Original SAP Transport Orders (TOs) originate here.
LO / Logis2 (Warehouse Execution & Orchestration Layer): Executes business intent from SAP into guided physical warehouse workflows. LO manages logical zones, user roles and rights, workflow state machines, pick-bin routing, internal container identities, printing, scale integrations, and station management console functions.
MFC / WAMAS-A (Material Flow Controller Layer): Controls and optimizes physical automation equipment. WAMAS-A interfaces directly with Programmable Logic Controllers (PLCs) via standardized protocols (such as SSI NGKP+), calculates dynamic conveyor routing, manages ASRS crane storage/retrieval queues, enforces physical area capacity limits, and monitors equipment status.
Physical System: Encompasses physical automation hardware and human operational spaces, including Very Narrow Aisle (VNA) turret trucks, Automated Storage and Retrieval System (ASRS) miniload cranes, automated AGV lanes, induction stations, conveyor loops, B/C pick stations, fast-pick flow racks, packing benches, and warehouse operators.

Information flows from left to right for execution instructions, while task confirmations, status updates, and quantity postings propagate back upstream from physical execution to SAP.

Core Operational Boundary Questions

System analysis and troubleshooting rely on four diagnostic questions:

What object is involved? (Material, Storage Unit/TUB, Picking Unit/TOTE, Handling Unit/HU, Delivery, Production Order, Transport Order, Location, Inventory Document).
Who owns the truth? SAP is the master system for warehouse stock quantities and core business master data. LO executes workflows and tracks logical process states. MFC/WAMAS controls equipment movement and automation execution.
What message or request crosses the boundary? Asynchronous business and document state changes use Intermediate Documents (IDOCs). Immediate, synchronous data validation or lookup requests require Remote Function Calls (RFCs).
What physical action must occur? A human operator, conveyor, ASRS crane, AGV, or forklift moves material. MFC coordinates automated machinery, while LO guides manual operator tasks around those movements.

Master System Logic and Inventory Ownership

SAP is the exclusive master system for inventory quantities. LO does not independently own stock counts or maintain an isolated inventory ledger; instead, LO queries SAP synchronously via RFC when real-time stock levels are required. If physical material exists in a bin but LO cannot display or allocate it, diagnostic investigation must begin in SAP to verify stock status, movement postings, and plant allocations.

Although SAP commands inventory strategy and master balances, LO converts high-level SAP intent into operational execution. A single business movement initiated in SAP (e.g., a delivery pick) may require multiple internal LO transport steps and several discrete physical MFC equipment instructions (e.g., retrieving a TUB to a B/C station, transferring picked items into a TOTE, routing the TOTE through fast-pick loops, and returning the non-empty TUB to ASRS storage).

Master Data, Warehouse Objects, and Strategy Ownership

Warehouse Terminology and Object Definitions

Warehouse management relies on precise definitions that distinguish moved materials, storage containers, picking vessels, and movement instructions:

Material: The article or product identity, managed and mastered in SAP. Material master records sync from SAP to LO via MATMAS IDOCs.
Storage Type: A logical warehouse subdivision containing storage bins (e.g., ASRS racking, VNA aisles, flow racks). Configured in SAP and mapped in LO for execution.
Storage Bin: A specific physical location within a Storage Type. The combination of Storage Type + Storage Bin defines a unique warehouse physical address (e.g., AU0 / 001-01-10).
Storage Unit (SU): A physical inventory container tracked by the warehouse. In ASRS vocabulary, a TUB is the primary Storage Unit.
TUB: The specific Storage Unit stored within and retrieved from the ASRS miniload racking. TUBs hold reserve inventory.
Picking Unit: A container used to accumulate picked items for outbound orders or production. In ASRS vocabulary, a TOTE is the primary Picking Unit.
TOTE: The specific Picking Unit that receives picked quantities at workstations. TOTEs travel along automated conveyors, through pick loops, to MTO assembly benches, and toward packing lines.
Handling Unit (HU): A physical transport container (e.g., shipping carton, parcel, or outbound pallet) built during repacking or staging for final shipping. Tracked in LO for shipping processes.
Transport Order (TO): An instruction directing material movement from a source location to a target location. Original warehouse TOs are generated in SAP, split or merged by LO into logical execution steps, and converted by MFC into physical equipment tasks.
Sector: A logical grouping of one or more Storage Types. Sectors control how TOs are split into manageable work packages and restrict user assignment.
Zone / Logical Location: Operational or temporary locations recognized by LO and MFC that do not exist as formal SAP storage bins (e.g., temporary staging zones, conveyor junction points, workstation endpoints, error lines).

System Distinction: TUB versus TOTE

TUB = Source Storage Unit: The ASRS stores inventory inside TUB containers. When demand occurs, MFC retrieves the TUB from miniload racks and presents it at a B/C station so operators can pick the required material.
TOTE = Destination Picking Unit: The warehouse operator places picked items into a TOTE container. The TOTE then navigates downstream conveyor loops to additional picking zones (AA/A fast pick), MTO assembly areas, staging loops, or packing stations.

This distinction explains why one high-level SAP TO can expand into multiple physical MFC movements: a TUB must travel from ASRS storage to a workstation, the destination TOTE must travel down the conveyor network, and the partially picked TUB must return to its ASRS rack location.

Roles and Sectors

User authorization and work placement are governed by Roles and Sectors:

Sectors define the physical or operational area of the warehouse (e.g., VNA aisles, ASRS B/C stations, Fast-Pick flow racks).
Roles define the functional permissions granted to a user (e.g., Goods Receiving, Material Handling, System Administrator).

A warehouse employee is assigned a Role that grants access to specific LO workflows, and assigned to Sectors that govern where they can receive and process Transport Orders.

Warehouse Strategy Ownership

Responsibility for warehouse operational strategies is allocated across system boundaries:

Strategy / Decision	System Owner	Functional Description	Assessment Anchor
Putaway Strategy	SAP	Determines target storage type, bin allocation strategy, and original putaway TO creation.	SAP owns Putaway Strategy
Replenishment Strategy	SAP	Calculates reorder thresholds, determines replenishment movement types, and issues replenishment TOs.	SAP owns Replenishment Strategy
Picking Strategy	SAP	Governs high-level inventory allocation (FIFO, batch selection, storage location selection).	SAP owns Picking Strategy
Manual Pick Sequence	LO	Sorts and sequences pick tasks within a TO for manual warehouse areas (VNA, flow rack racks) based on rack layout settings.	LO owns Manual Pick Sequence
ASRS Automated Pick Sequence	MFC	Optimizes automated miniload crane movements, conveyor routing, and physical retrieval sequences within ASRS.	MFC owns ASRS Pick Sequence

Interface Communication: IDOCs, RFCs, and Message Schemas

Asynchronous IDOCs vs. Synchronous RFCs

Data exchange between SAP, LO, and MFC follows a strict time-coupling design:

IDOC (Intermediate Document): Used for asynchronous transactional messages. IDOCs transfer structured business documents and state changes between systems. The sending application transmits the message and continues processing without waiting for immediate execution by the receiver. Examples include material master updates, order transmissions, movement postings, and TO confirmations.
RFC (Remote Function Call): Used for synchronous data requests. RFCs are executed when LO requires an immediate answer from SAP before proceeding to the next screen or workflow step. Examples include querying real-time stock balances, verifying target bin capacity, checking PLM material inspection status, and obtaining palletization standards.

IDOC Serialization and Key Objects

To prevent database lock contention in SAP when processing asynchronous messages, LO serializes outbound IDOCs based on key business objects. Key objects mapped per IDOC include:

MBGMCR: Reference document number, Material numbers
DELVRY: Delivery number, Purchase/Sales Order number
WMTCID: Transport Order number, Delivery number
SHPMNT: Delivery numbers

Inbound IDOC Queue Parallelization

Inbound IDOCs received by LO from SAP are processed through specialized parallel execution queues:

MasterData Queue (1 parallel queue): Processes MATMAS and CREMAS to maintain static master records in strict sequence.
Synchronizing Queue (10 parallel queues): Processes status updates and synchronization signals (ALEAUD, Z_LOGIS_SYNCHRON).
Process Queue (1 parallel queue): Processes operational transactional documents (ORDERS, DELVRY, OPERA, WMTOID, WMCAID, WMIVID) sequentially to prevent state conflicts.

Core IDOC Reference Table

IDOC Name	Description / Function	Direction	Operational Significance
`ORDERS`	Purchase Order Document	SAP $\rightarrow$ LO	Transmits inbound purchase order structures into LO.
`DELVRY`	Delivery Document	SAP $\rightleftharpoons$ LO	Bidirectional delivery creation, line update, and status sync.
`OPERA`	Production Order Document	SAP $\rightarrow$ LO	Transfers production order requirements and component lists to LO.
`SHPMNT`	Shipment Creation	LO $\rightarrow$ SAP	Transmits outbound shipment and handling unit structures to SAP.
`ALEAUD`	IDOC Processing Status Update	LO $\rightarrow$ SAP	Synchronizes processing status of upstream transactions.
`MBGMCR`	Multi-purpose Goods Movement	LO $\rightarrow$ SAP	Posts physical quantity movements (Goods Receipt, Goods Issue, Transfers).
`CONF`	Production Order Confirmation	LO $\rightarrow$ SAP	Confirms completed production orders and triggers finished goods receipt.
`WMBIID`	Lock / Unlock Location	LO $\rightarrow$ SAP	Posts physical bin or storage area lock/unlock changes to SAP.
`WMTOID`	Create Transport Order	SAP $\rightleftharpoons$ LO	Transmits original TO creation requests between SAP and LO.
`WMSUID`	Storage Unit Transport Order	LO $\rightarrow$ SAP	Requests transport creation for complete storage units.
`WMTCID`	Confirm Transport Order	LO $\rightarrow$ SAP	Confirms completed physical transport movements back to SAP.
`WMCAID`	TO Cancellation Request/Confirm	SAP $\rightleftharpoons$ LO	Synchronizes TO cancellations between systems.
`WMIVID`	Inventory Document Exchange	SAP $\rightleftharpoons$ LO	Transmits physical inventory count documents and posted results.
`MATMAS`	Material Master Data	SAP $\rightarrow$ LO	Integrates new and modified material master records from SAP into LO.
`CREMAS`	Creditor Master Data	SAP $\rightarrow$ LO	Transmits vendor and creditor master records to LO.
`Z_LOGIS_SYNCHRON`	Custom SAP Sync Status Update	SAP $\rightarrow$ LO	Updates LO on downstream SAP IDOC processing status.

Core RFC Reference Table

RFC Name	Purpose	Direction	Operational Cue
`IDOC