Troubleshooting OS Server Download Errors: 'RT Station Not Obtainable' and Target Directory Inaccessible in PCS 7

In SIMATIC PCS 7, the download errors 'RT Station not obtainable' and 'The target directory does not exist' during an OS Server download from the Engineering Station (ES) are caused by network communication failures or Windows sharing misconfigurations on the Terminal Bus. Specifically, these errors occur when: 1. The SIMATIC Shell is bound to the incorrect network adapter on the ES or OS; 2. Network name resolution fails between stations; or 3. The target OS directory is not shared with full read/write permissions for the 'SIMATIC HMI' user group. To resolve the errors, bind SIMATIC Shell to the Terminal Bus adapter on all stations, verify network visibility, share the destination OS folder with 'SIMATIC HMI' full control, and verify the UNC target path in SIMATIC Manager.

Executive Summary

Deploying compiled Operator Station runtime projects from the central Engineering Station to distributed OS Servers is a core engineering workflow in SIMATIC PCS 7. During this process, engineers frequently encounter blocking error dialogues such as RT Station not obtainable or The target directory does not exist. These errors halt project distribution and prevent online commissioning. Because OS downloads rely on a combination of proprietary Siemens communication protocols (SIMATIC Shell), Windows SMB network file sharing, and DCOM authentication, a single misconfiguration in network binding or folder permissions aborts the entire transfer. This article provides a systematic diagnosis and resolution guide to restore seamless ES-to-OS project downloads.

Architecture and Fundamental Mechanics

OS Download Protocol Stack, SIMATIC Shell Mechanics, and Windows Sharing Dependencies:

The Three-Tier Communication Stack of an OS Download:
Tier 1: Station Discovery (SIMATIC Shell): The ES locates target PC Stations using SIMATIC Shell multicast/broadcast telegrams over UDP port 5222. If SIMATIC Shell is bound to the wrong NIC (e.g. Plant Bus instead of Terminal Bus), the ES cannot discover the target station, triggering RT Station not obtainable.
Tier 2: Remote Configuration and Status Query (DCOM / RPC): The ES queries the remote station's WinCC runtime status via Remote Procedure Calls. If local Windows security policies or firewalls block DCOM ports (TCP 135 and dynamic RPC ports), the transfer is rejected.
Tier 3: File Copy and Database Attachment (SMB Network Shares): The compiled project files and SQL databases are copied over Windows File Sharing (SMB / TCP 445) to a shared network folder on the OS Server.
Root Causes of 'The target directory does not exist':
The UNC path specified in SIMATIC Manager under Target OS and Standby OS Computer points to a non-existent folder or invalid computer name (e.g. \\OS_SRV1\WinCC_Project where WinCC_Project is not shared).
The Windows network share exists, but the user account performing the download on the ES lacks write permissions in the share permissions or NTFS security permissions on the OS Server.
SIMATIC HMI Security Group Requirements:
Siemens WinCC strictly mandates that the Windows local group SIMATIC HMI must have Full Control permissions on the shared project destination folder across both ES and OS machines.

Step-by-Step Implementation Procedure

Configure and Verify SIMATIC Shell Network Binding:
* On both the Engineering Station and the OS Server, open Windows File Explorer.
* In the navigation pane, right-click SIMATIC Shell and select Settings.
* Verify that the selected network adapter is the dedicated Terminal Bus network interface card.
* Ensure Encrypted Communication settings match across all stations (if disabled on ES, it must be disabled on OS).
* Click OK. Expand SIMATIC Shell in File Explorer; confirm that all PC Stations (ES, OS Server 1, OS Server 2) are visible.
Verify Network Name Resolution and Connectivity:
* Open Windows Command Prompt on the ES; execute ping <OS_Server_Name>.
* Verify that the ping replies with the IP address of the OS Server's Terminal Bus interface.
* If ping fails or returns an unexpected IP address, update the C:\Windows\System32\drivers\etc\hosts file on both stations.
Configure Shared Folder and Permissions on Target OS Server:
* On the target OS Server, create or locate the target folder (e.g. D:\WinCC_Projects\Server1).
* Right-click the folder and select Properties > Sharing > Advanced Sharing.
* Check Share this folder and assign a share name (e.g. Server1_Project).
* Click Permissions; add the group SIMATIC HMI and assign Full Control.
* Switch to the Security tab (NTFS); add SIMATIC HMI and assign Full Control.
Verify Target Path in SIMATIC Manager on ES:
* In SIMATIC Manager Component View, right-click the OS object under the OS PC Station and select Object Properties.
* Select the Target OS and Standby OS Computer tab.
* In 'Path to the Target OS Computer', click Browse and locate the shared folder over the network (or enter \\<OS_Server_Name>\Server1_Project).
* Click OK to save.
Execute Download:
* Right-click the OS object and select PLC > Download.
* Select download scope (Entire OS or Changes) and observe the download complete successfully.

Verification

Initiate the OS download from SIMATIC Manager; verify that the project compilation status bar displays active file transfer.
On the OS Server, open the target directory and confirm that all WinCC project files (.mcp, databases, and graphics) have copied.
Confirm that SIMATIC Manager displays 'Download completed successfully' without RT station or target directory error dialogs.

Limitations and Operational Precautions

Downloading an OS project requires that the target computer name in the PCS 7 project matches the Windows computer name exactly (case-insensitive, but character-identical). If WinCC Runtime is currently active on the target OS Server, an 'Entire OS' download will be rejected; runtime must be deactivated first.

Engineer FAQ

What causes 'RT Station not obtainable' during OS download?

SIMATIC Shell bound to the wrong network adapter, network connectivity failure, or DCOM/firewall blocking communication.

Why does PCS 7 report 'The target directory does not exist'?

The target path in OS properties is misspelled, the network share does not exist, or the ES lacks write permissions to the folder.

Which user group must have permissions on the OS project folder?

The 'SIMATIC HMI' Windows user group must have Full Control in both Sharing and NTFS Security permissions.

How do I check if SIMATIC Shell is working?

Open Windows File Explorer, click SIMATIC Shell, and verify that all networked PCS 7 stations appear in the list.

Can I download an OS project over Wi-Fi?

No. PCS 7 strictly prohibits wireless connections for Terminal Bus and Plant Bus engineering and runtime downloads.

Technical References

OS Download

Simatic Shell

RT Station Not Obtainable

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Troubleshooting OS Server Download Errors: 'RT Station Not Obtainable' and Target Directory Inaccessible in PCS 7