Why Switching OS Compilation from AS-Oriented to Area-Oriented Causes Missing Tags

In SIMATIC PCS 7, when switching OS compilation mode from 'AS-oriented' to 'Area-oriented', process tags fail to generate on the WinCC OS Server if the Plant Hierarchy folders (Areas) are not explicitly mapped to that OS Server. In AS-oriented mode, the compiler transfers all S7 program blocks directly to the OS. In Area-oriented mode, the compiler evaluates the Plant Hierarchy, generating tags and alarms only for hierarchy folders assigned to the target OS via 'Plant Hierarchy -> Area -> OS Assignment'. Any unassigned area is completely skipped during compilation.

AS-Oriented vs. Area-Oriented OS Compilation Architecture

In SIMATIC PCS 7, the AS-OS Compile Wizard bridges the S7-400 controller software (CFC/SFC) and the WinCC Operator Station (OS). When compiling, the wizard extracts block parameters marked with operator control attributes (S7_m_c = 'true') and creates corresponding WinCC Structure Tags, raw communication tags, and Alarm Logging messages.

PCS 7 provides two distinct compilation modes:
1. AS-Oriented Compilation (Controller-Centric):
- The OS Compiler evaluates the S7 Program block directory of a specific Automation Station.
- It compiles 100% of all operator-controllable blocks residing in that controller directly into the target OS.
- Plant Hierarchy folder organization is ignored for tag routing.
2. Area-Oriented Compilation (Plant-Centric):
- Designed for multi-server, multi-unit distributed facilities where different OS Server pairs manage distinct physical plant sections (e.g. OS Server 1 governs Tank Farm; OS Server 2 governs Reactors).
- Tag generation is governed strictly by the Plant Hierarchy (PH).
- The compiler inspects each hierarchy folder designated as an Area and checks which OS Server is assigned to that Area.

The Role of Plant Hierarchy and OS Area Assignment

In SIMATIC Manager Plant View, the project hierarchy is organized into nested folders (e.g. Site -> Plant 1 -> Area A -> Unit 01 -> Equipment Phase).
* In the properties of any top-level hierarchy folder, the engineer can activate the checkbox: Hierarchy folder is an Area.
* When designated as an Area, an additional configuration tab appears: OS Assignment.
* In the OS Assignment tab, the engineer must explicitly select the target OS Server (e.g. OS(1) or OS_Redundant_Pair_A) responsible for visualizing and alarming that plant section.

Why Tags Disappear When Switching to Area-Oriented Mode

When an engineer switches compilation mode from AS-oriented to Area-oriented:
* Symptom: Compilation completes suspiciously quickly with zero errors, but upon opening WinCC Tag Management: Hundreds or thousands of tags are completely missing, or one server in a multi-server setup receives zero tags!
* Root Cause:
1. In AS-oriented mode, the OS Compiler never checked Area assignments; it simply mapped all charts in the AS to the OS.
2. When toggled to Area-oriented, the compiler checks the hierarchy tree. If hierarchy folders were created without checking Hierarchy folder is an Area, or if the OS Assignment dropdown was left unassigned (None), the compiler determines that zero tags belong to this OS Server.
3. Consequently, the compiler deletes existing tags from the WinCC database (marking them as obsolete) and generates zero new tags!

Compilation Scope and Mapping Mode Comparison Matrix

The following matrix compares AS-oriented and Area-oriented compilation modes:

Feature / MetricAS-Oriented CompilationArea-Oriented CompilationPrimary Routing SourceController S7 Program FolderPlant Hierarchy Folder StructureMulti-Server SplittingDifficult (1 AS = 1 OS Server)Native (1 AS can split across multiple OSs)OS Assignment DependencyCompletely IgnoredStrictly Mandatory per AreaMissing Area ConsequenceTags always compileTags are completely omitted from OSPicture Tree GenerationBasicDirectly mirrors Plant Hierarchy AreasRecommended ApplicationSingle-Server / Small PlantsStandard Multi-Server / Distributed Plants

Step-by-Step Procedure to Assign Areas and Recompile the OS

To restore missing tags and configure Area-oriented compilation:
1. Switch to Plant View in SIMATIC Manager:
- In SIMATIC Manager, select View -> Plant View.
- Expand your plant hierarchy to view all top-level process areas.
2. Configure Hierarchy Area Properties:
- Right-click the first process area folder (e.g. Raw_Materials) and select Object Properties.
- Under the General tab, check the box: Hierarchy folder is an Area.
3. Assign Target OS Server:
- Switch to the OS Assignment tab.
- In the dropdown menu, select the target OS Server project (e.g. OS_Server_A).
- Check the option Pass assignment down to all sub-folders.
- Click OK.
- Repeat this assignment for every Area folder in the plant hierarchy.
4. Configure Compilation Settings:
- Right-click the OS project in Plant View and select Compile.
- In the AS-OS Compile Wizard, select Area-oriented compilation mode.
- Under Scope, select Entire OS (mandatory when changing compilation modes to rebuild complete tag mappings).
5. Execute OS Compilation and Verification:
- Click Compile. Allow the wizard to parse the plant hierarchy.
- When finished, open WinCC Explorer on the OS Server and verify that all structure tags, internal tags, and alarm messages populate the database.

Verification

Verify that all process tags are restored in WinCC:
1. Open WinCC Explorer on the target OS Server.
2. Open Tag Management: Under the Named Connections channel unit, verify that all S7 structure tags for motors, valves, and analog transmitters are present.
3. Open Alarm Logging: Verify that message lines exist for all technological blocks across the assigned areas.
4. Open Picture Tree Manager: Verify that the plant hierarchy areas display as top-level navigation container buttons matching the Plant View tree.

Limitations and Operational Precautions

Switching compilation modes between AS-oriented and Area-oriented requires compiling the Entire OS; compiling 'Changes only' will leave orphaned tag structures in the database.
If a single CFC chart contains blocks belonging to different physical plant areas, split the chart into modular charts matching physical hierarchy boundaries.
Never leave high-level hierarchy folders unassigned in Area-oriented mode; unassigned folders will drop all nested measurement points from the operator system.

Engineer FAQ

Can a single Automation Station (AS) feed multiple OS Servers in Area-oriented mode?

Yes. This is the primary benefit of Area-oriented mode: an S7-400 controller executing logic for both Area A and Area B can route Area A tags to OS Server 1 and Area B tags to OS Server 2 seamlessly.

Why did the Picture Tree disappear after changing compilation mode?

The WinCC Picture Tree is generated directly from the Plant Hierarchy. If hierarchy folders lose their Area status or OS assignment, the Picture Tree generator cannot build the hierarchy navigation bar.

Can I use Area-oriented compilation with single-station OS projects?

Yes. Area-oriented compilation is the standard recommended mode for all modern SIMATIC PCS 7 systems, including single-station OS deployments, to ensure clean plant hierarchy alignment.