Technical Restrictions on Hosting SIMATIC PCS 7 Multiprojects on Network-Attached Storage (NAS)

Hosting an active SIMATIC PCS 7 Multiproject on Network-Attached Storage (NAS) and opening it directly from an Engineering Station over a network share is strictly unsupported by Siemens and results in extreme latency (taking 5 to 10 minutes per tree click) and database corruption. A PCS 7 Multiproject is not a static file store; it contains multiple concurrent relational databases (Microsoft SQL Server and Sybase) requiring low-latency NTFS opportunistic locking and local transaction logging that standard NAS appliances (Linux CIFS/SMB) cannot deliver. For multi-user engineering, Siemens mandates hosting the project locally on an enterprise Windows Server Engineering Station with local NVMe/SSD storage, using NAS appliances strictly for passive backup archives.

Why Network-Attached Storage (NAS) Fails with PCS 7 Databases

To simplify project sharing across engineering teams, system integrators sometimes attempt to place an uncompressed SIMATIC PCS 7 Multiproject directly onto a commercial Network-Attached Storage (NAS) appliance or shared corporate file server, accessing the project over a Gigabit Ethernet link from client Engineering Stations.

While Gigabit Ethernet provides 125 MB/s bandwidth, opening the project takes 5 to 10 minutes, and browsing technological folders triggers persistent application freezes. Investigation into PCS 7 database architecture explains this failure:

Database SubsystemStorage Mechanism in MultiprojectBehavior Over Standard NAS Share (SMB / CIFS)Microsoft SQL Server (WinCC)Relational tables (.mdf, .ldf)SQL Server strictly prohibits mounting database files over remote SMB network sharesSybase / S7 Database EngineEmbedded relational database filesGenerates millions of micro-file I/O requests; CIFS metadata latency causes 5-minute freezesNTFS File Locking & OplocksTransactional integrity locksLinux Samba/CIFS emulation cannot provide deterministic Windows NTFS locking, corrupting headersSimaticShell AccessSecurity token RPC queriesNAS appliances cannot execute Siemens DCOM security hooks or join SIMATIC HMI groups

Because an active project requires tens of thousands of sub-millisecond file transactions during basic navigation, network file latency cripples SIMATIC Manager.

Architectural Requirements for Multi-User Engineering

For facilities requiring multiple automation engineers to program separate controllers or technological areas simultaneously, Siemens defines a strictly certified Multi-User Engineering architecture:

Dedicated Central Engineering Server (ES Server):
- The Multiproject is stored exclusively on local high-speed storage (enterprise NVMe or SAS SSDs) of a dedicated PC Station running a certified Windows Server operating system.
- The host system runs local instances of Microsoft SQL Server and Sybase.
Distributed Engineering Clients (ES Clients):
- Client PCs access the shared project over the Terminal Bus using SimaticShell and Windows sharing permissions.
- All participating stations must have identical PCS 7 versions, identical service packs, and identical library updates.
Project Branching / Check-Out Workflow:
- For optimal speed and safety, individual subprojects (e.g. AS_02) are checked out locally (Project -> Remove from Multiproject), engineered locally at full SSD bus speed, and merged back into the master multiproject (File -> Multiproject -> Insert Project) upon completion.

Step-by-Step Procedure to Set Up Supported Central Engineering

To migrate away from an unsupported NAS setup and establish a high-performance central engineering server, follow this workflow:

Archive and Relocate Project from NAS: In SIMATIC Manager on the ES, execute File -> Archive. Save the compressed ZIP package locally. Delete the uncompressed project folders from the NAS.
Designate Central ES Server: Select an Engineering Station with high single-core CPU frequency, 16+ GB RAM, and high-speed local SSD storage. Retrieve the project archive onto local drive D:\SIEMENS\STEP7\S7Proj\.
Configure Windows Sharing and Permissions: Share the project directory over the network. Grant full access permissions to the local Windows user groups: SIMATIC HMI, SIMATIC HMI CS, and Administrators.
Configure SimaticShell Across All Engineering Stations: On the ES Server and all ES Client workstations, open SimaticShell. Verify that all PCs can see each other with blue active icons and zero communication errors.
Use NAS Strictly for Passive Long-Term Backups: Configure scheduled archiving scripts (e.g. weekly automated PKZip backups) to push compressed .zip archives to the NAS. The NAS serves as a disaster recovery vault, never an active runtime disk.

Verification

Confirm project access performance and database integrity through these operational benchmarks:

Multiproject Open Latency: In SIMATIC Manager, open the shared project from an ES Client. Confirm that the project tree loads in under 15 seconds (compared to 5 minutes on the NAS).
CFC Navigation Responsiveness: Double-click multiple CFC charts across different AS projects. Confirm that charts open instantaneously within 2 to 3 seconds.
Consistency Check Verification: In SIMATIC Manager, execute File -> Check Consistency. Confirm that all cross-project technological connections and S7 databases evaluate with 0 Errors.

Limitations and Operational Precautions

When architecting engineering networks for PCS 7, observe these critical operational constraints:

Never Store Live SQL Databases on Network Shares: Microsoft explicitly denies warranty support for SQL Server databases hosted on remote SMB shares for interactive transaction processing.
Plant Bus Direct Connection Mandatory for Loading: While engineering navigation occurs over the Terminal Bus, any ES station performing direct controller downloads or online monitoring must be connected directly to the Plant Bus (via CP 1623 or Softnet-IE); routing AS downloads through an intermediate ES Server is prohibited.
Version Symmetry: Ensure all engineering laptops and workstations share the exact same hardware catalog updates and optional packages (e.g. PDM, S7 F Systems) to prevent project database corruption.

Engineer FAQ

Why can I store CAD drawings or Office files on a NAS, but not a PCS 7 project?

CAD and Office files are static, single-file documents read entirely into memory upon opening. PCS 7 projects are active relational databases that continuously execute concurrent random-access disk read/writes with microsecond latency requirements.

Can I map a drive letter (e.g. Z:) to the NAS to make PCS 7 think it is local?

No. Mapping a network drive letter does not alter the underlying network transport protocol; Windows still accesses the drive via SMB/CIFS over TCP/IP, retaining all latency and locking bottlenecks.

Is it safe to use a NAS to store project archives created with File -> Archive?

Yes, absolutely. Compressed archive files (.zip) are single static files that can safely be stored, replicated, and backed up on any commercial NAS or cloud storage repository.