Resolving Missing api-ms-win-crt-string-l1-1-0.dll on Windows Server 2012 R2 During PCS 7 V9.0 Installation

The error 'api-ms-win-crt-string-l1-1-0.dll is missing' during SIMATIC PCS 7 V9.0 installation on Windows Server 2012 R2 occurs because the operating system lacks the Microsoft Universal C Runtime (Universal CRT). The Universal CRT is an essential operating system component introduced in Windows 10 and required by the modern Visual C++ libraries deployed across PCS 7 V9.0. To resolve the failure, two prerequisite Microsoft update packages must be installed in exact sequential order before launching PCS 7 setup: First, KB2919355 (Windows Server 2012 R2 Update rollup). Second, KB2999226 (Update for Universal C Runtime in Windows). Although Microsoft download titles reference 'Windows 8.1', both updates share the exact same NT 6.3 kernel binary and are fully compatible with Windows Server 2012 R2.

The Role of Universal C Runtime (CRT) in SIMATIC PCS 7 V9.0

With the release of SIMATIC PCS 7 V9.0, Siemens modernized the underlying runtime architecture across engineering and server components. Core services, Microsoft SQL Server 2014, and communication drivers were recompiled against the Microsoft Visual C++ 2015/2017 toolchain. Applications compiled with these modern compilers depend on the Universal C Runtime (Universal CRT), which encapsulates standardized C library functions into dynamic-link libraries prefixed with api-ms-win-crt-*.dll.

While Windows 10 includes the Universal CRT as a native operating system component, older operating systems—specifically Windows 7 SP1, Windows 8.1, and Windows Server 2012 R2—do not possess these runtime libraries out of the box. If an engineer installs PCS 7 V9.0 on a raw Windows Server 2012 R2 build that lacks recent servicing updates, system setup abruptly fails with: The program can't start because api-ms-win-crt-string-l1-1-0.dll is missing from your computer.

Why Microsoft Update Packages Reference Windows 8.1 on Server 2012 R2

Engineers frequently express concern when Microsoft download links for Server 2012 R2 display titles such as 'Windows 8.1 Update (KB2919355)'. In Microsoft's operating system architecture, Windows Server 2012 R2 and Windows 8.1 share the identical underlying Windows NT 6.3 operating system kernel codebase.

Prerequisite UpdateMicrosoft Package IdentifierPurpose in PCS 7 InstallationKernel DependencyServicing BaselineKB2919355Major platform update rollup for NT 6.3Mandatory prerequisite for all subsequent Server 2012 R2 updatesUniversal CRTKB2999226Installs Universal C Runtime binaries (api-ms-win-crt-*.dll)Requires KB2919355 to be installed firstVisual C++ RedistVC++ 2015-2019 RedistributableInstalls C++ application runtime engineRequires active Universal CRT

Attempting to install KB2999226 on a vanilla Server 2012 R2 machine without KB2919355 will fail with the error: 'The update is not applicable to your computer'.

Step-by-Step Installation Procedure (KB2919355 and KB2999226)

To prepare Windows Server 2012 R2 for a seamless SIMATIC PCS 7 V9.0 deployment, execute the following sequence:

Reboot and Clear Pending Operations: Reboot the server and verify in Windows Update that no pending installation tasks are in progress.
Install KB2919355: Download and install the update package for KB2919355. Ensure that prerequisite patch KB2919442 is present if prompted by the installer. Reboot the server when installation finishes.
Install KB2999226: Download and install KB2999226 (Update for Universal C Runtime in Windows). Execute wusa.exe as Administrator. Reboot the server upon completion.
Alternative Offline Method: The SIMATIC PCS 7 V9.0 DVD 2 media includes the required Microsoft redistributables in Support\MS_Updates. Installing from this local folder ensures exact tested versions are deployed.
Launch PCS 7 Setup: Open the PCS 7 V9.0 media and execute Setup.exe. Verify that the system readiness check passes all operating system prerequisite tests without DLL warnings.

Verification

Confirm that the Universal CRT is properly installed and functioning using these checks:

File System Verification: In Windows Explorer, navigate to C:\Windows\System32\. Confirm that api-ms-win-crt-string-l1-1-0.dll and ucrtbase.dll are present and possess valid digital signatures.
Installed Updates Audit: Open PowerShell and run Get-HotFix -Id KB2919355, KB2999226. Verify that both hotfixes return an installed status with valid installation dates.
PCS 7 Setup Execution: Run PCS 7 Setup. Proceed through component selection; verify that SQL Server 2014 and AS-OS Engineering packages install to 100% completion without aborting.

Limitations and Operational Precautions

When patching server operating systems in PCS 7 plants, observe these guidelines:

Siemens Tested Updates Compatibility: As mandated in Siemens Industry Online Support FAQ Entry ID 109749345, never enable automatic Windows Updates on production PCS 7 servers. Install only Microsoft updates explicitly validated by Siemens for your specific PCS 7 release.
Redundant Server Synchronicity: When applying OS updates to a redundant OS Server pair, update Server B while Server A remains Master, confirm redundancy synchronization, then switch mastership and update Server A.
Commercial Procurement and Licensing Disclaimer: Windows Server 2012 R2 operating system licenses and Client Access Licenses (CALs) must be procured through authorized Microsoft OEM or volume licensing channels. Ensure hardware vendor procurement schedules account for sufficient CAL counts.

Engineer FAQ

Why didn't the PCS 7 installer install KB2999226 automatically?

The PCS 7 installer attempts to install redistributables; however, Windows Update standalone packages (.msu) cannot install if the Windows Update service is disabled or if prerequisite servicing stack updates (like KB2919355) are missing.

Can I just copy api-ms-win-crt-string-l1-1-0.dll from another PC?

No. The api-ms-win-* files are API forwarders that point to ucrtbase.dll and low-level kernel routines. Simply copying the file without installing the official Windows update will result in entry-point error 0xC000007B.

Is Windows Server 2012 R2 still supported for new PCS 7 installations?

PCS 7 V9.0 originally released on Server 2012 R2; however, modern PCS 7 releases (V9.0 SP3, V9.1) recommend Windows Server 2016 or 2019 for extended lifecycle support.