Understanding and Managing the Master Data Library in SIMATIC PCS 7 Multiprojects

The Master Data Library (MDL) in SIMATIC PCS 7 is the centralized, project-specific repository that serves as the single source of truth for all technological blocks, Control Module Types (CMT), SFC Types, and Shared Declarations used across a Multiproject. Identified by a blue icon in SIMATIC Manager, the MDL prevents block number conflicts (e.g. duplicate FB numbers), standardizes library versions, and enables plant-wide type-instance synchronization. When engineering in CFC, engineers must drag blocks exclusively from the Master Data Library rather than standard system libraries. When blocks or types are updated in the MDL, executing 'Update Block Types' automatically propagates changes across all AS subprojects in the Multiproject.

Executive Summary

In large-scale SIMATIC PCS 7 distributed control systems, engineering is divided across multiple automation stations (AS) and distinct engineering teams. Without centralized governance, individual programmers frequently import disparate library versions, introduce custom function blocks with overlapping block numbers (e.g. FB250 used for two completely different functions), or create uncoordinated equipment types. The Master Data Library (MDL) provides the foundational architectural mechanism in STEP 7 to enforce plant-wide standardization. This article explains the technical role of the Master Data Library, details the creation and population workflow, and outlines best practices for type-instance synchronization.

Architecture and Fundamental Mechanics

Master Data Library Architecture and Type-Instance Synchronization:

Multiproject Modularity and Block Conflict Hazards:
A PCS 7 Multiproject aggregates multiple independent AS and OS subprojects.
If each subproject imports standard libraries independently (e.g. APL, Industry Library, CEMAT), minor version differences can create catastrophic compilation conflicts during cross-AS communication or OS compilation.
Furthermore, custom user blocks can inadvertently collide on identical FB/FC numbers, causing memory corruption or silent block overwrites during AS download.
Master Data Library as the Single Source of Truth:
The Master Data Library (indicated in SIMATIC Manager by a distinctive blue library icon) acts as the exclusive clearinghouse for the entire multiproject.
It contains four primary folders:
1. Blocks Folder: Hosts all approved FB, FC, and DB blocks. Duplicate block numbers are detected and resolved here using the STEP 7 'Rewire' function.
2. Charts Folder: Stores master template charts, Control Module Types (CMT), Equipment Module Types (EMT), and Equipment Phase Types (EPHT).
3. SFC Types Folder: Contains standardized sequential state machine types.
4. Shared Declarations: Centralizes enumerations, units, and equipment properties across all controllers.
Type-Instance Synchronization Mechanism:
When a block, SFC Type, or CMT is modified in the Master Data Library, the engineer executes Options -> Charts -> Update Block Types in CFC.
The synchronization engine scans all AS projects in the Multiproject, compares block timestamps and interfaces, and updates all instantiated blocks in place while preserving user parameter assignments.

Step-by-Step Implementation Procedure

Create and Designate the Master Data Library:
* If the multiproject was created with the PCS 7 'New Multiproject' Wizard, an MDL is created automatically.
* To designate an existing library as the MDL manually: In SIMATIC Manager Component View, right-click the library, navigate to Multiproject, and select Define as Master Data Library.
* Confirm that the library icon turns from green to blue.
Populate the Master Data Library with System Blocks:
* Select File -> Open and click the Libraries tab.
* Open the PCS 7 Advanced Process Library (e.g. PCS 7 AP Library V90).
* Open the Blocks folder of the APL, select all required blocks (or Ctrl+A to select all), and copy them.
* Switch to your Master Data Library's Blocks folder and paste the copied blocks.
* Repeat this process for any additional approved libraries (e.g. SFC Library, Basis Library, Industry Library).
Engineering with the Master Data Library in CFC:
* Open any CFC chart in an AS subproject.
* In the CFC block catalog (left pane), click the library dropdown and select your Master Data Library.
* Drag blocks into charts exclusively from the MDL catalog. Never drag blocks from standard system libraries directly.
Synchronizing Block Type Updates Across Subprojects:
* When a block or type is upgraded in the MDL:
* Open any CFC chart, select Options -> Charts -> Update Block Types.
* In the dialog box, select the target AS projects within the Multiproject.
* Review the list of modified blocks and interface changes.
* Click OK to execute automatic synchronization across all selected projects.
Resolving Block Conflicts Using the Rewire Utility:
* If two custom blocks collide on the same block number (e.g. FB500):
* In the MDL, select Options -> Rewire.
* Assign an unused block number to the colliding block, and update all references.

Verification

Verify Master Data Library Integrity and Consistency:
1. In SIMATIC Manager Component View, confirm that the Master Data Library icon displays with a blue background.
2. Execute Options -> Charts -> Update Block Types with 'Check only'; confirm that all subprojects report 0 block inconsistencies or version mismatches.
3. Perform a full CFC compilation across all AS projects; verify clean compilation without duplicate block number errors.

Limitations and Operational Precautions

Operational Precautions and Library Discipline:
- A Multiproject can have only one designated Master Data Library at any time; never create multiple conflicting MDLs.
- Never modify block algorithms directly inside individual AS subprojects; always modify the source block in the Master Data Library and synchronize downward to protect type-instance integrity.
- Modifying block interfaces (adding/removing pins) in the MDL requires an AS compilation with memory reset or careful delta compilation planning to avoid unexpected controller stops.

Engineer FAQ

Why does the Master Data Library have a blue icon while others are green?

The blue icon signifies that the library has been designated as the active 'Master Data Library' for the Multiproject. Standard libraries have green icons.

Can I have more than one Master Data Library in a Multiproject?

No. A Multiproject supports exactly one Master Data Library. You can switch the designation to another library by deselecting 'Define as Master Data Library' and assigning a new one.

What happens if I drag a block directly from the APL library into a chart?

Dragging blocks from outside the MDL breaks centralized version control. If the system library is patched later, that chart will not receive coordinated updates during multiproject synchronization.

How do I update block types across six different AS projects simultaneously?

In CFC, select Options -> Charts -> Update Block Types, select all six AS projects in the dialog, and execute the synchronization pass.

What are Shared Declarations in the Master Data Library?

Shared Declarations contain standardized enumerations, units of measurement, and equipment properties shared across all AS controllers and WinCC OS stations in the plant.