Understanding PCS 7 Multiproject Directory Naming on Disk vs SIMATIC Manager Display Names

In SIMATIC PCS 7, the physical directory names created on the Windows file system for multiprojects and subprojects often differ from the descriptive names visible in SIMATIC Manager because STEP 7 derives on-disk folder names using legacy 8-character naming rules. When a multiproject is created, STEP 7 generates folders ending in '_MP' (multiproject), '_Lib' (master data library), and '_Prj' (subproject). For subsequent subprojects, Windows folder names are truncated to the first 8 characters of the project name, and duplicates append '(1)'. Renaming folders directly in Windows File Explorer is strictly prohibited because it corrupts internal database pointers; proper folder alignment must be performed using 'File -> Save As...' in SIMATIC Manager.

Executive Summary

When engineering large-scale automation architectures in SIMATIC PCS 7, developers create multiprojects containing multiple automation subprojects (e.g. Boiler_Area, Turbine_Area, Water_Treatment) and master libraries. When browsing the physical storage directory in Windows File Explorer, engineers are frequently dismayed to find truncated, abbreviated, or cryptically indexed folder names (such as BOILER_A, TURBINE_, or BOILER(1)), while SIMATIC Manager displays full, elegant project names. Attempting to 'fix' this by renaming folders directly in Windows Explorer destroys the project database, rendering it unopenable. This article explains the internal file storage philosophy of STEP 7, details how folder names are generated, and outlines the approved method to achieve clean on-disk directory structures.

Architecture and Fundamental Mechanics

STEP 7 Relational File System, 8.3 Naming Heritage, and Multiproject Pointer Mechanics:

The 8-Character File System Heritage in STEP 7:
The core database architecture of SIMATIC STEP 7 / PCS 7 was historically developed during the Windows NT / FAT era, incorporating internal dBase III/IV and Sybase structures.
To ensure cross-compatibility with legacy communication drivers and toolchains, STEP 7 maintains a strict rule: Physical on-disk project directory names are derived from the first 8 characters of the project name.
Standard Directory Generation Rules in the 'New Project Wizard':
When creating a multiproject named Plant2021:
- Plant2021_MP: The root directory containing the multiproject definition files (.s7m).
- Plant2021_Lib: The Master Data Library folder containing shared block types and templates (.s7l).
- Plant2021_Prj: The first automation project folder (.s7p).
When a new subproject is added (e.g. Reactor_Unit_A):
- STEP 7 truncates the name to the first 8 characters: Reactor_.
If a second project is added sharing the same prefix (e.g. Reactor_Unit_B):
- STEP 7 truncates to the first 5 characters and appends a numeric counter: React(1).
Display Names vs Physical Folder Names:
Inside the project database file (<Project>.s7p), STEP 7 stores the full user-defined Display Name (up to 24 characters).
SIMATIC Manager displays this rich metadata name in the project tree, while the underlying physical directory retains its abbreviated 8-character folder name.
Why Direct Windows Renaming Causes Catastrophic Failure:
The master multiproject file (.s7m) stores exact relative file paths to every constituent subproject's .s7p file.
If an engineer renames a folder in Windows File Explorer (e.g. changing React(1) to Reactor_Unit_B), the multiproject's internal path pointers become broken.
Upon opening the multiproject in SIMATIC Manager, the subproject appears greyed out with a red slash, reporting: 'Project cannot be found'.

Step-by-Step Implementation Procedure

Best Practice for Creating New Projects with Clean Folder Names:
* When adding a new project to a multiproject in SIMATIC Manager:
* Right-click the Multiproject root -> Insert New Object -> Project.
* In the creation dialog, do NOT rely on default path generation.
* In the Storage location (path) field, manually type the desired clean folder name (e.g. C:\Projects\Plant_MP\Reactor_A).
* By explicitly typing the path, STEP 7 creates the directory with the exact specified name rather than an 8-character abbreviation.
Aligning Folder Names for Existing Truncated Projects:
* If an existing project has an undesirable folder name (e.g. React(1)):
* In SIMATIC Manager, select the subproject in the tree.
* Select File -> 'Save As...'.
* In the 'Save Project As' dialog:
- Under Name, enter the clean display name.
- Under Storage location (path), click Browse and create a clean target folder name (e.g. Reactor_Unit_A).
- Ensure the option Add to current multiproject is checked.
- Click OK.
- STEP 7 copies the entire project database into the newly named directory and automatically updates all multiproject pointers.
Removing the Old Truncated Subproject:
* In SIMATIC Manager, select the old subproject with the ugly folder name.
* Select File -> Manage -> Multiproject -> Remove from Multiproject.
* Open Windows File Explorer and delete the old orphaned directory (React(1)).

Verification

Open Windows File Explorer; browse to the multiproject storage path.
Confirm that all project folders now display clean, recognizable, descriptive folder names.
Launch SIMATIC Manager; open the multiproject.
Verify that all subprojects and the Master Data Library open cleanly without missing project warnings.

Limitations and Operational Precautions

Never use special characters (such as %, &, !, @, #) or spaces in project folder names on disk, as older Siemens compilers and command-line utilities (e.g. S7-SCL or CFC batch tools) may fail when parsing paths containing spaces. Keep the total path length under 128 characters to avoid Windows MAX_PATH truncation issues.

Engineer FAQ

Why does STEP 7 truncate folder names to 8 characters on disk?

Because STEP 7 maintains historical 8.3 file system conventions to ensure compatibility across internal database engines.

Can I rename project folders directly in Windows File Explorer?

No! Renaming folders in Windows breaks internal relational pointers, causing SIMATIC Manager to report that the project cannot be found.

What does the _MP folder stand for?

_MP designates the master Multiproject container directory holding the .s7m linking database.

What does the _Lib folder stand for?

_Lib designates the Master Data Library containing shared technological block types and SFC templates.

How do I rename a project folder safely?

Use File -> Save As... in SIMATIC Manager, specify the new clean path, and select 'Add to current multiproject'.

Technical References

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Understanding PCS 7 Multiproject Directory Naming on Disk vs SIMATIC Manager Display Names