Standard Best Practices for Creating a New Multiproject in SIMATIC PCS 7: AS, OS, and Library Structure

In SIMATIC PCS 7, standard engineering best practice dictates creating a Multiproject containing segmented sub-projects: a dedicated AS project for controllers, an OS project for servers/clients, and a Master Data Library (MDL) consolidating all APL blocks and templates. Never build plants inside a standalone single project. Use the PCS 7 'New Project' Wizard to generate the initial framework, configure Plant Hierarchy levels, and populate the Master Data Library.

Multiproject Architecture vs. Standalone Single Projects

When commencing a new process automation project in SIMATIC PCS 7, beginner engineers often make a fundamental structural mistake: creating a standard, monolithic single project (File > New... > Project).

In standard STEP 7 Classic, single projects are common. In SIMATIC PCS 7, however, standalone single projects are strictly an anti-pattern:
* Engineering Scalability: A single project cannot be efficiently split across multiple engineers working simultaneously over a network.
* Compilation and Database Overhead: Storing automation stations, multiple redundant OS servers, and master libraries in a single project database creates bloated files prone to corruption during concurrent access.
* Cross-Station Communication: NetPro cross-project connections, Master Data Library synchronization, and Plant Hierarchy derivations require a Multiproject structure.

Siemens mandates structuring every automation facility as a SIMATIC PCS 7 Multiproject, which serves as an overarching umbrella binding multiple autonomous sub-projects and a centralized Master Data Library together.

Segmented Multiproject Structure and Component Distribution

According to SIMATIC PCS 7 Compendium Part A, enterprise facilities should segment their multiproject into functional sub-projects:

Automation Station Sub-Project (AS_Project):
* Contains the SIMATIC S7-400 or CPU 410-5H controllers, decentralized I/O racks (ET 200SP HA, ET 200M), and the S7 Program container.
* Houses all CFC charts, SFC charts, and hardware configurations.
* On large plants, multiple AS sub-projects can be created (e.g. AS_Unit1, AS_Unit2).
Operator Station Sub-Project (OS_Project):
* Contains the SIMATIC PC Stations: OS Single Stations, Redundant OS Server pairs, and OS Clients.
* Houses WinCC graphics (.pdl), scripts, Tag Management, and Alarm Logging archives.
Master Data Library (Master_Data_Library - MDL):
* The central repository for the entire facility.
* Blocks Folder: Contains master copies of all APL blocks, driver blocks, and custom user FBs.
* Templates Folder: Contains master Control Module Typicals (Process Tag Types).
* Shared Declarations: Global enumeration types, units of measurement, and equipment properties.
Engineering / Client Station Sub-Project (Optional for Large Plants):
* Dedicated sub-project housing client terminal layouts and engineering station configurations.

Step-by-Step Multiproject Creation Workflow Using the Wizard

1. Launch the PCS 7 'New Project' Wizard

Open SIMATIC Manager.
Select menu File > 'New Project' Wizard....
In the introductory screen, click Next.

2. Select Controller and Hardware Architecture

Select the target CPU from the list (e.g. CPU 410-5H or CPU 414-5H).
Configure communication interfaces: select Industrial Ethernet (CP 443-1 / PN) and assign initial subnet addresses.
Click Next.

3. Configure Plant Hierarchy and Software Objects

Select the number of Plant Hierarchy Levels (standard: 3 to 4 levels, e.g. Plant > Unit > Function).
In the OS configuration step: select SIMATIC PC Station (OS Single Station / Server).
Recommendation: Deselect the automatic insertion of sample CFC/SFC charts to keep the initial project clean.
Click Next.

4. Name the Multiproject and Finalize Creation

Enter the multiproject name (e.g. MP_ChemicalPlant).
Specify the directory path on a high-speed local drive (never directly on an unmapped network share).
Click Finish. The wizard automatically generates:
* MP_ChemicalPlant (Multiproject container)
* AS_Project (Hardware & S7 Program)
* OS_Project (PC Station & WinCC)
* Master_Data_Library (Empty central repository)

5. Populate the Master Data Library from APL

Open the PCS 7 AP Library (File > Open > Libraries).
Copy all required blocks from the APL Blocks folder into the Master Data Library Blocks folder.
Copy required typicals from APL Templates into the Master Data Library Templates folder.
Open the AS project CFC editor; select Options > Block Types... and import the blocks from the Master Data Library into the AS program.

PCS 7 Multiproject Sub-Project Structure Matrix

Sub-Project / ContainerPrimary Elements ContainedPrimary Engineering TasksShared Across Team?Multiproject RootCross-project NetPro links, Cross-referencesMultiproject management, Cross-compileTop-level project umbrellaAS_Project(s)S7-400/CPU 410, Distributed I/O, CFC, SFCPLC programming, Interlocks, SequencingChecked out to AS engineersOS_ProjectOS Servers, OS Clients, WinCC databaseMimic design, Alarm scripting, FaceplatesChecked out to HMI/SCADA engineersMaster_Data_LibraryMaster Blocks, Typicals, Shared DeclarationsTemplate governance, Version baseliningRead-only access; modified by Lead Engineer

Verification

In SIMATIC Manager, confirm the project tree displays the multiproject icon with three sub-nodes: AS Project, OS Project, and Master Data Library.
In the Master Data Library, verify the Blocks folder contains official APL blocks.
Open NetPro at the multiproject level; verify network subnets (Terminal Bus and Plant Bus) span cleanly across both the AS and OS projects.
In the AS project, open a CFC chart and insert an APL block from the Master Data Library; verify block imports without version conflicts.
Execute PLC > Compile and Download Objects; confirm initial project compilation completes with 0 Errors.

Limitations and Operational Precautions

Never Work Across Remote Network Shares: Never open and edit a PCS 7 multiproject directly across a standard Windows file share over high-latency networks. Multi-user engineering requires local check-out/check-in workflows or centralized version management (Version Trail).
Single Master Data Library Rule: A multiproject must contain exactly one Master Data Library. Defining multiple libraries creates ambiguity during module driver generation and block updates.
Plant Hierarchy Consistency: Ensure the identical Plant Hierarchy settings (number of levels, OS area assignment) are maintained across both the AS and OS sub-projects.

Engineer FAQ

Can I split a single AS project into multiple AS projects later?

Yes. SIMATIC Manager allows creating additional projects within the multiproject (File > Multiproject > Create New Project) and moving AS stations between projects using drag-and-drop.

Why is the Master Data Library required if APL is already installed on the PC?

The Master Data Library guarantees project independence. When the project is archived and sent to another site, the Master Data Library preserves the exact block versions utilized, preventing mismatches if the other PC has a different library hotfix installed.