PCS 7 v8.1 WinCC Trend Properties Storage: Files and Config

Overview of PCS 7 WinCC Trend Property Storage

When an operator changes trend display properties (color, time range, pens, scaling) during runtime in a Siemens PCS 7 v8.1 OS, the persistence behavior of those changes is governed by the WinCC OnlineTrendControl. The location, file format, and per-user separation of those trend properties changed significantly between PCS 7 V6/V7.0 and PCS 7 V7.1 SPx / V8.x. This article documents the on-disk locations, the runtime behavior behind each option in the Online configuration tab, the user-specific profile folder, and the procedure to restore an engineer's "original" properties after an operator modifies them on shift.

The information below applies to PCS 7 V8.1 and the corresponding WinCC V7.x runtime that ships inside the PCS 7 installation. References are made to the PCS 7 Process Control System manuals and the WinCC Information System.

Trend File Format and Folder Location: Before vs. After V7.1

WinCC trends used by the OnlineTrendControl and the more recent WinCC Online Trend Control (OCX) are persisted on the local engineering / server station in the project directory.

The TRG subfolder is created automatically by WinCC Explorer the first time the Graphics Designer compiles or opens a picture containing an OnlineTrendControl. Even though the folder name still says "TRG" (a legacy artifact from the .TRG era), the files inside are now named *.TRC. The path on a typical PCS 7 OS server looks like:

If you do not see the TRG folder, compile the OS once from the PCS 7 project (right-click the OS in SIMATIC Manager → OS → Compile) and the directory is created. The TRC files are loaded by the WinCC runtime when the picture is opened; they are also the source used by the Graphics Designer when a project is opened in configuration.

OnlineTrendControl "Online configuration" Tab Options

Open the picture containing the OnlineTrendControl in Graphics Designer, double-click the control, then select Properties → Online configuration. The three radio buttons define how the operator's runtime changes are handled:

Do not retain — the operator's change applies to the live trend display only; the next time the picture is loaded, WinCC reads the original TRC from the TRG folder and discards the operator's modifications.

Retain during runtime — the change is written to the in-memory representation of the trend; it persists as long as the WinCC Runtime process is alive. A picture change preserves the change, but a clean exit of WinCC Runtime (RT\_PM.exe / RT\_PCS7.exe) or a server reboot drops it.

Retain permanently — the change is written to disk into the user-specific profile folder (see next section). It survives picture changes, runtime restarts, and OS server reboots. This is the only option that materially persists the operator's modifications.

User-Specific Storage: The "Profiles" Folder

With the new controls for Tag Logging and Alarm Logging that became available in WinCC V7.0, runtime changes to controls are no longer stored in a single shared file. Each change is now associated with the WinCC user that is currently logged in, and persisted under:

Concrete path on a PCS 7 V8.1 OS server:

The file inside that folder is named exactly like the picture (PDL) that contains the control, with no extension. It is a small XML containing only the property overrides applied at runtime. Multiple controls inside the same picture store their overrides in the same file.

Restoring the Engineer's Original Trend Properties

The original trend properties configured by the engineer in Graphics Designer are stored in the .TRC file inside the TRG folder. To restore those originals after an operator has changed them with Retain permanently, perform the following steps on the OS server (or OS client that owns the picture):

1. Stop WinCC Runtime on the affected station (open WinCC Explorer → File → Exit WinCC Explorer, or stop the "WinCC Runtime" service).
2. Navigate to <Project>\Profiles\<UserName>\.
3. Locate the file that matches the picture name (e.g., Overview.Pdl).
4. Delete this file (or rename to *.bak as a safety copy).
5. Optionally also delete the matching entry in <Project>\Profiles\<UserName>\<UserName>.urf if you want a clean slate for that user.
6. Restart WinCC Runtime.

On restart, WinCC cannot find the per-user override, so it falls back to the engineering values stored in the .TRC file inside the TRG folder. The picture now displays with the original colors, time range, pens, and limits as configured by the engineer.

Project Folder Layout Diagram (SVG)

Activating Alarm Logging and Tag Logging in PCS 7 V8.1

PCS 7 automatically generates WinCC alarms and archive tags from CFC blocks that support the OCM (Operator Control and Monitoring) capability. To make sure the runtime actually publishes and records these, both Alarm Logging Runtime and Tag Logging Runtime must be enabled in the OS server's startup list.

Alarm Logging Runtime

1. On the OS server, open WinCC Explorer.
2. Right-click the computer name under Computer and select Properties.
3. Switch to the Startup tab.
4. In the WinCC Runtime Start up Order list, check the box next to Alarm Logging Runtime.
5. Click Apply, then OK. The activation requires a restart of WinCC Runtime.

Tag Logging Runtime

Tag Logging Runtime is enabled by default in the WinCC Runtime Start up Order of a PCS 7 OS server. Verify by following the same procedure as above and confirming that the Tag Logging Runtime entry is checked. If you disabled it during earlier maintenance, re-enable it and restart runtime.

Configuring Tag Archive Properties on a CFC Parameter

Each OCM-capable block parameter can be individually marked for archiving. The configuration is performed in the CFC editor:

1. Open the CFC chart that contains the block (e.g., an APL block such as OpDi01, MotSpd, VlvAnl, etc.).
2. Right-click the desired parameter (for example SetOp on OpDi01) and select Object Properties.
3. Switch to the Archive tab.
4. Select one of the three options listed below.
5. Compile the OS so the archive tag is created in WinCC Tag Logging.

The default option for most APL blocks is Archiving. Switch to Long-term archiving only when a Process Historian is part of the system architecture. Selecting Long-term archiving on an OS that is not connected to a PH will still create the local archive tag; the values are stored locally but not forwarded.

TagLogging Segment, Size, and Backup Configuration

Inside WinCC Explorer → Tag Logging editor, each archive can be tuned to match disk budget and retention rules. The most important parameters are:

• Segment size (MB or number of datapoints): when the active segment reaches the configured size, the runtime rolls a new segment and starts writing into it.
• Segment time period: the maximum lifetime of one segment (e.g., one day, one week, one month) before it is closed.
• Backup path: location where closed segments are moved for long-term storage. Point this to a network share that is included in your backup cycle. The runtime continues to write to the local segment while the backup copy is created.
• Swap behavior: when the configured maximum number of segments is reached, the oldest segment is either overwritten (ring archive) or the runtime stops accepting new values (linear archive). Ring archive is the default for PCS 7 process value archives.

For full details, open the WinCC Information System within the OS server and navigate to Working with WinCC → Archiving Process Values. The same content is mirrored in the printed PCS 7 Operator Station manual set.

Verification Procedure After Restoring Trend Properties

1. Confirm the .TRC file still exists in the project's TRG folder and is readable.
2. Confirm the user-specific override file was deleted (or renamed to .bak).
3. Restart WinCC Runtime and log in as the affected operator user.
4. Open the picture that contains the OnlineTrendControl.
5. Verify visually that the trends show the engineering colors, time range, pen selection, and Y-axis scaling.
6. Modify one property as the operator (e.g., zoom in to 10 minutes), then close the picture and reopen it. With Retain permanently, the change is preserved; with Do not retain, the engineering values come back immediately.
7. Check that the operator's profile file is regenerated under Profiles\<User>\ when Retain permanently was used.

Troubleshooting Matrix

Notes on PCS 7 V8.1 vs. Newer PCS 7 Versions

PCS 7 V8.1 and V8.2 use the same TRC / Profiles storage scheme described above. PCS 7 V9.0 introduced WinCC Unified (TIA Portal-based HMI) as a parallel runtime; Unified uses a different storage model entirely (a database-backed configuration store) and the .TRC / Profiles mechanism only applies to the classic WinCC Runtime (sometimes called "WinCC Professional Classic" or simply "WinCC RT"). If you migrate specific pictures to Unified, the file locations and per-user override behavior change accordingly and are not covered by this article.