Writing WinCC V7 Tag Values to External SQL Server Database

1. Overview: The WinCC-to-External-SQL Challenge

Siemens SIMATIC WinCC V7.0 SP3 stores runtime, alarm, and tag-logging data inside a project-bound Microsoft SQL Server instance. The internal archive database is held in exclusive single-user mode while Runtime is active. When a higher-level application such as SAP, a custom MES, or a reporting tool needs to consume or write the same tag values that the HMI sees, the engineer must build an explicit bridge from WinCC to a user-managed SQL Server.

WinCC does not provide an "open this database" channel to user applications by default. Three production-proven paths exist:

• Industrial Data Bridge (IDB) - separately licensed option that runs as a Windows service, configured through a graphical designer.
• VBScript inside WinCC - scripts executed by the WinCC scheduler that read tag-logging archives via the WinCC OLE DB Provider and push rows into an external SQL Server using ADO/ODBC.
• Connectivity Pack / OPC UA Server - exposes WinCC tags via standardized interfaces; the external consumer writes directly through the OPC layer.

2. WinCC Database Architecture Recap

Understanding which WinCC subsystem owns which data prevents wasted engineering effort:

The tag-logging database uses a proprietary compression scheme on archived segments. Reading "raw" values requires the WinCC OLE DB Provider; standard T-SQL SELECT against the MDF file is not supported.

3. Method Comparison

Recommendation: Use Industrial Data Bridge for routine archive forwarding. Use VBScript when you need conditional logic, transformations, or trigger-based writes (e.g., event-driven push to SAP on alarm). Use Connectivity Pack / OPC UA when the consumer is already OPC-capable or needs bidirectional live tag access.

4. Industrial Data Bridge: Architecture and Provider Matrix

Industrial Data Bridge is configured through the WinCC IDB Designer. A configuration consists of one or more connections (each with a source and a destination provider) plus a transfer object that defines the field mapping and schedule.

Common providers shipped with IDB:

5. Industrial Data Bridge: Step-by-Step Setup

5.1 Prerequisites

1. WinCC V7.0 SP3 Upd1 or later with valid license key on the engineering station and on the Runtime station that will host IDB.
2. Microsoft SQL Server 2008 R2 or newer (Express is sufficient for small archives; Standard/Enterprise for > 4 GB).
3. ODBC Driver 11 for SQL Server (or native client) installed on the IDB Runtime station.
4. User account with db_datareader/db_datawriter on the target database, or a dedicated SQL login with a strong password.
5. TCP port 1433 (default) open between IDB host and SQL Server; if named instance, also UDP 1434.
6. WinCC project activated at least once so tag-logging segments exist.

5.2 Create the Destination Table in SQL Server

CREATE DATABASE WinCC_Export;
GO
USE WinCC_Export;
GO
CREATE TABLE dbo.TagHistory (
    Id          BIGINT IDENTITY(1,1) NOT NULL PRIMARY KEY,
    TagName     NVARCHAR(128) NOT NULL,
    TagValue    SQL_VARIANT NULL,
    Quality     INT NOT NULL,
    Timestamp   DATETIME2(3) NOT NULL,
    SourceTime  DATETIME2(3) NULL
);
CREATE INDEX IX_TagHistory_TagName_Time
    ON dbo.TagHistory(TagName, Timestamp DESC);
GO
CREATE USER [WINCCSVC] FOR LOGIN [WINCCSVC];
ALTER ROLE db_datareader  ADD MEMBER [WINCCSVC];
ALTER ROLE db_datawriter  ADD MEMBER [WINCCSVC];
GO

Using SQL_VARIANT for TagValue avoids schema rework when WinCC tag types change. The composite index supports the typical "last value per tag" query the downstream SAP consumer runs.

5.3 Configure the ODBC DSN on the IDB Host

1. Open ODBC Data Sources (64-bit) from Control Panel → Administrative Tools.
2. Add a System DSN named DSN_WinCC_Export pointing to WinCC_Export on the SQL Server using SQL Server authentication.
3. Test the connection; if it fails with "Cannot open database requested by login", confirm the login's default database is set to WinCC_Export in SQL Server Management Studio.

5.4 Configure IDB Connection Pair

1. Open the WinCC Explorer → Industrial Data Bridge on the IDB Runtime host.
2. Right-click Connections → New Connection. Name it WinCC_to_SQL.
3. Add a source provider: WinCC Archive Provider. Set the WinCC project path, choose the tag-logging archive, and pick the tag(s) to forward. Use SELECT Tag, Value, Quality, Timestamp FROM <archive> syntax.
4. Add a destination provider: ODBC Provider. Select the DSN_WinCC_Export DSN, set the target table to dbo.TagHistory.
5. Map the WinCC fields to the SQL columns. Type-cast Value → TagValue as SQL_VARIANT.

5.5 Define the Transfer

1. Right-click Transfers → New Transfer. Link it to the WinCC_to_SQL connection.
2. Set the trigger to On Change for live tags or Cyclic every 10 s for archived history. The minimum cycle in IDB V7 is 1 second.
3. Enable Write buffer with size 500 rows to batch inserts; this reduces SQL Server transaction overhead by an order of magnitude.
4. Save the configuration; IDB compiles it into an XML file under <WinCC Project>\IDB\.
5. Start the IDB Runtime Service from Windows Services or via net start "Siemens Industrial Data Bridge".

5.6 Verify

In SQL Server Management Studio, run:

SELECT TOP 20 TagName, TagValue, Quality, Timestamp
FROM dbo.TagHistory
ORDER BY Timestamp DESC;

Rows must appear within the configured cycle. If the table stays empty, check the IDB Runtime log at C:\ProgramData\Siemens\Automation\IDB\Logs\.

6. VBScript with WinCC OLE DB Provider

Use this method when you need conditional forwarding, transformations, or event-driven writes the IDB designer cannot express. The script runs inside WinCC Runtime, so it stops if Runtime stops.

6.1 Connection Strings

' WinCC archive read (local Runtime)
strArchive = "Provider=WinCCOLEDBProvider.1;" & _
             "Catalog=CC_EngineeringR_140531_113122;" & _
             "Data Source=.\WinCC"
' Replace the catalog name with the actual project archive.
' Find it in WinCC Explorer → Tag Logging → Properties → Archive name.

' External SQL Server write
strTarget  = "Provider=SQLNCLI11;" & _
             "Server=SQLSRV01\INSTANCE01;" & _
             "Database=WinCC_Export;" & _
             "Uid=winccsvc;" & _
             "Pwd=StrongP@ssw0rd;"

For named instances, escape the backslash as \\ inside the connection string.

6.2 Reading WinCC Archives

Dim connArc, rsArc, sql
Set connArc = CreateObject("ADODB.Connection")
connArc.CursorLocation = 3   ' adUseClient
connArc.Open strArchive

sql = "SELECT TOP 1 'Tank1.Level', RealValue, Quality, Timestamp " & _
      "FROM dbo.Tank1_Level_Archive " & _
      "WHERE Timestamp > '2024-01-01 00:00:00.000' " & _
      "ORDER BY Timestamp DESC"

Set rsArc = CreateObject("ADODB.Recordset")
rsArc.Open sql, connArc

If Not rsArc.EOF Then
    Dim sTag, vVal, iQual, dtTs
    sTag  = rsArc.Fields(0).Value
    vVal  = rsArc.Fields(1).Value
    iQual = rsArc.Fields(2).Value
    dtTs  = rsArc.Fields(3).Value
    ' ... forward to external DB
End If

rsArc.Close
connArc.Close

6.3 Writing to External SQL Server

Dim connOut, cmd
Set connOut = CreateObject("ADODB.Connection")
connOut.Open strTarget

Set cmd = CreateObject("ADODB.Command")
cmd.ActiveConnection = connOut
cmd.CommandText = "INSERT INTO dbo.TagHistory " & _
                  "(TagName, TagValue, Quality, Timestamp) " & _
                  "VALUES (?, ?, ?, ?)"
cmd.Parameters.Append cmd.CreateParameter("TagName",  202, 1, 128, sTag)   ' adVarWChar
cmd.Parameters.Append cmd.CreateParameter("TagValue",  12,  1,   0, vVal)   ' adVariant
cmd.Parameters.Append cmd.CreateParameter("Quality",   3,   1,   0, iQual)  ' adInteger
cmd.Parameters.Append cmd.CreateParameter("Timestamp", 7,   1,   0, dtTs)   ' adDate
cmd.Execute

connOut.Close

6.4 Scheduling the Script

Open WinCC Explorer → Global Script → Actions. Create a new action named Forward_TagHistory, paste the code, and trigger it with a cyclic event (default 1 s, recommended 5-10 s for archive forwarding). The action runs in the WinCC scheduler and survives Runtime restarts as long as the project is reloaded.

7. Connectivity Pack and OPC UA Alternative

When the external consumer (SAP, custom MES) is already OPC-capable, expose WinCC via the WinCC OPC UA Server (part of the Connectivity Pack option). Configuration steps:

1. Install the Connectivity Pack V7.0 SP3 on the WinCC Runtime station.
2. Enable OPC UA Server in WinCC Explorer → Communication → OPC UA WinCC.
3. Define a server endpoint at opc.tcp://<Runtime>:48020 and select a security policy (None for test, Basic128Rsa15 or higher for production).
4. Tag mapping: the OPC UA namespace mirrors WinCC internal tag names with dot-to-underscore translation (for example, Tank1.Level → Tank1_Level).
5. On the SAP side, configure an OPC UA client (or an OPC-to-XML gateway) to subscribe to the tags. SAP Plant Connectivity (PCo) is the most common bridge.

This path requires the consumer to handle OPC UA authentication, certificate trust, and subscription keep-alive. Latency is typically 100-500 ms over LAN, acceptable for SCADA but too high for closed-loop control.

8. SAP Integration Patterns

SAP consumes process data via PCo (Plant Connectivity) using XML-based queries. The two supported topologies with WinCC V7 are:

For bidirectional tag write-back (SAP writes a recipe parameter that WinCC must apply to the PLC), the OPC UA path is mandatory: WinCC tags marked as writable in the OPC UA configuration accept incoming writes, which WinCC then forwards to the PLC via the configured channel (MPI/Profibus/Profinet).

9. SQL Server Sizing and Tuning

For a plant producing 5,000 process tags with 1 s archive cycle, plan for:

Apply partitioning by day or week once the table exceeds 100 million rows. A partitioned clustered index on Timestamp lets SAP drop old partitions in seconds.

10. Verification and Commissioning Checklist

1. Confirm WinCC Runtime is active and tag-logging segments are written (check WinCC Explorer → Tag Logging → Archive).
2. Confirm SQL Server target database WinCC_Export exists with the schema above.
3. Confirm the IDB or VBS service account can authenticate to SQL Server.
4. Trigger a known tag change at the PLC and observe the row appear in dbo.TagHistory within the configured cycle.
5. Force-stop the IDB service and restart; rows buffered before the stop must appear after the restart (transactional guarantee).
6. From the SAP PCo side, execute a test query and confirm rows return with the expected TagName and Timestamp.
7. Run a 24-hour burn-in and check the SQL Server transaction log growth, CPU, and disk queue length against baseline.

11. Troubleshooting Matrix

FAQ