WinCC Alarm Logging: Populating Username on Acknowledgement

Problem Statement

When a runtime user acknowledges an active alarm in a Siemens WinCC HMI/SCADA project, the Alarm Logging control correctly creates an acknowledgement row, but the "User name" column remains blank. The Date, Time, and Count columns populate automatically because the Alarm Logging editor inserts them by default; the User name field is only populated when the Alarm Logging editor has been told where to find it. The symptom is most commonly observed on WinCC V7.x projects that have replaced the internal WinCC user administration with the central SIMATIC Logon service, but the same fault pattern appears on WinCC Professional (TIA Portal) projects when the logged-in Windows user is supplied through a UMC, AD, or SIMATIC Logon back end.

The fault is not a bug in Alarm Logging. It is a configuration gap. Alarm Logging needs two distinct settings before it will copy the runtime user into the acknowledgement row: (1) a system block assignment that includes the User name block, and (2) a process value block (or an internal tag) that supplies the actual name. When SIMATIC Logon is the identity provider, the standard @CurrentUser and @CurrentUserName tags do reflect the Windows-authenticated user, so the fix is straightforward once the binding chain is understood.

Root Cause Analysis

Alarm Logging writes an acknowledgement record whenever the runtime calls AXC_OnAcknowledge() (WinCC V7 C-API) or whenever the user clicks the acknowledgement button bound to Acknowledge in the Alarm Logging OCX. The internal handler writes the timestamp from the runtime clock, increments the Count counter, and copies the current username from a tag that has been pre-bound to the message frame.

Three preconditions must all be satisfied for the username column to be non-empty:

1. The internal tag that contains the user identity (@CurrentUserName or a project-specific tag) must currently hold the SIMATIC Logon-resolved identity. WinCC re-reads this tag on every acknowledgement event; it is not cached.
2. The alarm message class must have a process value block slot bound to that tag using the @N%s@ syntax (for example @102%s@ for block 2). The "contains expanded associated values" property of the message must be enabled, otherwise the placeholder is stored literally rather than evaluated.
3. The User name system block must be added to the Alarm Logging view. System blocks are separate from process value blocks; they govern which Alarm Logging control columns exist and which Alarm Logging fields they display.

If any one of the three preconditions is missing, the column will be blank even though the acknowledgement itself succeeds. This is by design: Alarm Logging never invents a username, it only displays the value it was handed.

Configuration Prerequisites

Step-by-Step Resolution

1. Confirm SIMATIC Logon Is the Active Identity Provider

1. In the WinCC Explorer, right-click User Administrator and open its properties.
2. Open the Logon tab. Verify the dropdown "Use SIMATIC Logon for logon" is selected. If unchecked, the runtime falls back to the internal user list and the @CurrentUser tag will read from that internal list instead.
3. Open the Windows Services console (services.msc) on the runtime PC and confirm the SIMATIC Logon service status is Running and startup type is Automatic.
4. Open SIMATIC Logon Configuration from the Start menu. Validate that the project is listed under "Assigned WinCC projects" and that the operator's Windows group has been granted the alarm acknowledgement authorization.

2. Validate @CurrentUser and @CurrentUserName Are Populated

1. In the WinCC Explorer, open Tag Management → Internal Tags.
2. Confirm the tags @CurrentUser (text tag, 255 chars) and @CurrentUserName (text tag, 255 chars) exist. Both are created automatically by the WinCC runtime; do not delete them.
3. Start the runtime, log on with a SIMATIC Logon user, and add a temporary I/O field bound to @CurrentUserName to verify the display name appears. If the field stays empty, the SIMATIC Logon service is not connected to the project; revisit Step 1.

3. Bind the User Name to a Process Value Block

Alarm Logging reads the username through a process value block placeholder. The default message classes ship with up to 10 process value blocks; the conventional choice for the username is block 10 (placeholder @10%s@) or block 2 (@2%s@) if you want to keep the user in the message text as well.

1. In the WinCC Explorer, open Alarm Logging and select the message class that contains the alarms you need (typically System - Errors or a custom class).
2. Right-click the class → Properties → Process Values tab.
3. In the row for the desired block index (for example, Block 10), enter the placeholder @10%s@ in the message text column if you want the user to appear in the alarm text, and in the Process Value column reference the tag @CurrentUserName.
4. Click Apply and close the dialog.

4. Enable "Contains Expanded Associated Values" on the Message

This is the property most often missed. Without it the @N%s@ placeholder is stored as a literal string and never expanded at runtime, regardless of the tag binding.

1. In Alarm Logging, select the individual message (or Ctrl-A to select all messages in the class).
2. Open Properties → Parameters/Options tab (WinCC V7) or the equivalent Message properties pane in WinCC Professional.
3. Enable the checkbox "Contains expanded associated values" (German: "Erweiterte Begleitwerte enthalten").
4. Click Apply and commit the change to the project database.

5. Add the User Name System Block to the Alarm Control

The system block is the column-level switch; the process value block is the data source. You need both.

1. In the Graphics Designer, open the picture that contains the WinCC Alarm Control (OCX) and double-click it.
2. Click the toolbar button Select columns (or right-click the control → Configure columns).
3. In the dialog "Add/Remove..." select Available System Blocks → User name.
4. Click the transfer (right-arrow) button to move it to Selected System Blocks.
5. Position the column where you want it (between Time and Text is conventional), confirm with OK.
6. Save the picture and re-compile / re-activate the runtime.

6. Optional: Add a Comment Column for Audit Trail

For FDA 21 CFR Part 11 / GxP installations, the alarm acknowledgement event needs the operator identity, a timestamp, and ideally an optional comment. Add the Comment system block the same way you added User name, and configure the control to prompt for a comment on acknowledgement via the OCX property Acknowledge with comment.

Verification Procedure

After applying the changes, verify end-to-end with this checklist. Do not skip any step; each verifies a different part of the chain.

1. Runtime identity test: Bind an output field to @CurrentUserName. Confirm the displayed name matches the SIMATIC Logon user. If it does not, the remaining steps will fail silently.
2. Trigger test alarm: From the Graphics Designer or a script, trigger an alarm that is a member of the modified message class. Confirm the alarm row appears with the configured user name in its text and acknowledgement column.
3. Acknowledge test: Click the Acknowledge button. The User name column of the acknowledgement row must contain the same value displayed in Step 1.
4. Audit database test: If the project archives to SQL, open MS SQL Server Management Studio, expand the alarm archive database, run SELECT * FROM dbo.MS_AlarmView WHERE UserName IS NOT NULL ORDER BY TimeStamp DESC and confirm the UserName column is populated for new rows but empty for legacy pre-change rows.
5. Multi-user test: Log out, log in with a second SIMATIC Logon account, repeat the acknowledgement test. Both usernames must appear independently.

Process Value Block Syntax Reference

The placeholder grammar in Alarm Logging is @<block>%<format>@. The block index selects one of the ten process value blocks bound to the message class; the format specifier tells Alarm Logging how to render the value.

Block 0 is reserved by Alarm Logging for the message number and cannot be reassigned. Blocks 11 and above are not supported in the default message classes; if more are needed, create a custom message class with additional blocks defined in its property sheet.

System Block Reference

System blocks are the columns visible in the Alarm Control. They are managed in two places: the column selection dialog of the Alarm Control OCX, and the Alarm Logging editor's System Blocks node. The relevant system blocks for this fix are:

WinCC Professional / TIA Portal Equivalent

The same logic applies in TIA Portal WinCC Professional, but the menus differ. The mapping below helps engineers moving projects from V7 to V17/V18.

Cross-Platform Alarm Acknowledgement Models

Other major HMI/SCADA platforms solve the same problem with different architectural primitives. Engineers responsible for multi-vendor sites should understand the parallel mechanisms so they can debug in any environment.

AVEVA's documentation is explicit: "The acknowledge request contains the user's name and any alarm comment. For the alarm utility, the alarm is acknowledged within the alarm feature immediately." This is the same handshake WinCC implements, just with the user identity attached at a different layer of the stack.

Troubleshooting Matrix

Diagnostic Queries and Scripts

For VBScript-based diagnostics inside WinCC, the following snippet dumps the active user identity into a status line so you can confirm the tag chain without leaving runtime:

' WinCC V7 VBScript - log current user to a diagnostic tag
Dim sUser, sHost
sUser = HMIRuntime.Tags("@CurrentUserName").Read
sHost = HMIRuntime.Tags("@CurrentUser").Read
HMIRuntime.Trace "User=" & sUser & " Host=" & sHost & " Time=" & Now

For projects that need to write the user to a non-default process value block, set the binding programmatically when the operator logs in:

' Bind operator name to block 10 of the active alarm message
Sub OnLogon(sUser)
    HMIRuntime.Tags("OperatorName_PB10").Write sUser
End Sub

SQL Archive Verification

WinCC stores alarm events in the SQL Server alarm database (default name CC_Alarming_<ProjectName>_<Timestamp>). After the fix is deployed, confirm the archive integrity:

-- Top 20 acknowledgement events, newest first
SELECT TOP 20
    TimeStamp,
    MsgProcID,
    State,
    UserName,
    ComputerName,
    Comment
FROM dbo.MS_AlarmEvents
WHERE State = 4   -- 4 = acknowledged
ORDER BY TimeStamp DESC;

-- Count of acknowledgement events missing user identity
SELECT COUNT(*) AS BlankUserNameAcks
FROM dbo.MS_AlarmEvents
WHERE State = 4
  AND (UserName IS NULL OR LTRIM(RTRIM(UserName)) = '');

The State column uses the bitmask documented in the WinCC Alarm Logging SQL reference: 1 = came, 2 = went, 4 = acknowledged, 8 = commented. Audit queries should always filter on State & 4 = 4 to isolate acknowledgement-only rows.

Performance and Retention Notes

Each acknowledgement row is one SQL insert; on a high-noise plant with 50 000+ alarms per shift, the MS_AlarmEvents table grows roughly 50 MB per week. The username column is a fixed nvarchar(60) so it adds negligible storage. Retention is governed by the archive configuration in Alarm Logging → Archive Configuration. For GxP sites, configure no automatic deletion and enable SQL Server transparent data encryption on the database files.

Bind @CurrentUserName to a single process value block and reuse it across all message classes where possible. Each binding adds a single tag read per acknowledgement event; reusing one binding keeps the runtime overhead flat as the project grows.

Safety and Compliance Considerations

In plants under FDA 21 CFR Part 11 or EU GMP Annex 11, the alarm acknowledgement record constitutes an electronic signature linking an operator identity to a process event. Two controls are mandatory on top of the WinCC configuration:

1. The Windows account used to log on to SIMATIC Logon must itself be unique to the operator (no shared accounts). Configure the SIMATIC Logon Configuration tool to enforce individual accounts; group-based authentication alone is insufficient for the electronic signature rule.
2. The audit trail in MS_AlarmEvents must be write-protected at the SQL role level. Revoke UPDATE and DELETE on this table from the WinCC runtime account; grant only INSERT and SELECT.

References to Official Documentation

For deeper reading, refer to:

• Siemens WinCC V7.5 SP2 Alarm Logging manual (entry ID 109750604 on the Siemens Industry Online Support portal at support.industry.siemens.com) — the canonical reference for process value block syntax and system block semantics.
• Siemens SIMATIC Logon V1.6 administration manual — describes the credential provider plug-in that writes @CurrentUser and @CurrentUserName.
• Inductive Automation Ignition User Manual, section system.alarm.acknowledge — alternative implementation for comparison.
• AVEVA Application Server documentation, alarm acknowledgement page — confirms the parallel user/comment data flow.

FAQ