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Increasing Alarm Display and Buffer Limits in CEMAT V8.2 and WinCC Alarm Control

Increasing Alarm Display and Buffer Limits in CEMAT V8.2 and WinCC Alarm Control

In SIMATIC PCS 7 CEMAT V8.2, the operator alarm list is visually capped at 1,000 messages because the default configuration of the WinCC Alarm Control (@AlarmControl) restricts simultaneous row queries to 1,000 messages to maintain operator station responsiveness. To increase the display and retention limit to 1,500 alarms or more, engineers must adjust two distinct settings: expand the Short-Term Archive buffer capacity in WinCC Alarm Logging properties from 1,000 to the desired limit, and modify the WinCC Alarm Control properties on the CEMAT alarm page (@C_Alarm.pdl) to increase the maximum query limit on the Selection / Query tab, followed by saving the graphic template.

Table of Contents

WinCC Alarm Control Display Limits vs Short-Term Archive Buffers

In SIMATIC PCS 7 CEMAT installations, continuous monitoring of heavy industrial machinery (crushers, ball mills, rotary kilns, bucket elevators) generates significant volumes of technological alarm records. The operator alarm visualization system consists of two decoupled components:

  1. The WinCC Alarm Logging Engine: An underlying SQL Server service managing the Message Buffer (active alarms in memory) and the Short-Term Archive (time-sliced circular buffer storing past alarms).

  2. The WinCC Alarm Control (@AlarmControl): The graphical table control embedded inside the CEMAT alarm picture (@C_Alarm.pdl or @C_Alarm_Overview.pdl).

A common misunderstanding is assuming the visual limit dictates how many alarms the system actually saves. While SQL Server may store tens of thousands of alarms, the graphical control restricts the active visual query to 1,000 lines to prevent client interface freezing during alarm floods.

Why the Alarm List Defaults to 1,000 Messages

Siemens intentionally enforces a default limit of 1,000 displayed messages in the WinCC Alarm Control for critical operational and architectural reasons:

  • SQL Query Execution Time: Querying more than 1,000 rows across distributed multi-server networks over the Terminal Bus introduces graphical latency. When an operator switches to the alarm screen during an emergency, a massive un-indexed query can freeze the client for several seconds.
  • Human Cognitive Bandwidth: International alarm management standards (EEMUA 191 / ISA-18.2) demonstrate that an operator cannot cognitively evaluate 1,000 simultaneous alarms. The proper operational practice is utilizing time-range, area-based, or priority filters.
  • Buffer Allocation: If an engineering team explicitly requires a larger active buffer (e.g., 1,500 alarms), both the SQL buffer and the front-end control query limit must be synchronized.

Alarm Buffer and Control Display Parameter Matrix

The following table compares configuration parameters governing alarm retention and visual limits:

Configuration ParameterLocationDefault ValueAdjusted TargetOperational PurposeShort-Term Archive BufferWinCC Alarm Logging -> Properties1,000 messages1,500 to 5,000Retains recent alarms in RAM / SQL bufferMax Displayed RowsWinCC Alarm Control -> Selection Tab1,000 messages1,500 rowsSets visual row limit in table gridLong-Term Archive SegmentationArchive Configuration -> Message ArchiveDaily / 1 GBMonthly / 2 GBDetaches historical archive segmentsAlarm Buffer Filter CriteriaAlarm Control ToolbarNone (All)Filtered by AreaEnhances rendering speed during floods

Step-by-Step Configuration to Expand the Alarm Limit to 1,500 Messages

To increase the CEMAT alarm list limit from 1,000 to 1,500 messages:

  1. Expand Short-Term Archive in WinCC Alarm Logging:
    - On the Engineering Station or OS Server, open WinCC Explorer.
    - Open Alarm Logging.
    - In the navigation pane, right-click Messages -> select Message Archive Properties.
    - Locate the setting for Max. number of messages in the short-term archive.
    - Increase the limit from 1000 to 1500 (or 2000).
    - Save and close Alarm Logging.

  2. Modify WinCC Alarm Control in CEMAT Graphic Template:
    - In WinCC Explorer, open Graphics Designer.
    - Open the CEMAT alarm picture @C_Alarm.pdl (or project-specific alarm picture).
    - Double-click the WinCC Alarm Control object to open its properties.
    - Select the Selection (or Performance) tab.
    - Locate the parameter Maximum number of messages to be loaded (or query limit).
    - Change the limit from 1000 to 1500.
    - Save the picture file.

  3. Compile and Download to OS Servers / Clients:
    - In SIMATIC Manager, perform a Changes-Only OS Compile.
    - Download the updated project to the OS Servers and OS Clients.
    - In WinCC Runtime, open the alarm screen; the table will now populate up to 1,500 active and historical entries.

Verification

Verify expanded alarm list behavior:
1. In WinCC Runtime, open the CEMAT alarm screen.
2. Switch the view from 'Active Alarms' to 'Short-Term Archive' (Archivliste).
3. Inspect the status bar at the bottom of the Alarm Control; confirm that the message counter displays counts exceeding 1,000 (e.g., 1480 / 1500).
4. Scroll to the bottom of the table to confirm that historical records past the previous 1,000 mark are fully visible.
5. Verify that screen switching between process graphics and the alarm list remains snappy without graphical lag.

Limitations and Operational Precautions

  • Client Rendering Overhead: Expanding the alarm control query beyond 2,000 messages will noticeably degrade screen callup times on older client PCs or multi-screen operator consoles.
  • Alarm Flooding Risks: If a plant routinely exceeds 1,500 active alarms, the core problem is an alarm flood rather than a display limit; implement ISA-18.2 alarm rationalization and suppression.
  • CEMAT Template Overwrites: Re-running the OS Project Editor with 'Update Picture Files' enabled will restore factory templates; protect customized @C_Alarm.pdl files.

Engineer FAQ

Can the WinCC Alarm Control display an unlimited number of messages?

While the control can be configured without limits, doing so is strongly discouraged. Querying tens of thousands of rows causes severe SQL Server lockouts and freezes the WinCC client.

What happens to alarms after they exceed the short-term archive limit?

Older alarms are detached from the circular short-term buffer and transferred into long-term archive segments (.mdf/.ldf) managed by ArchiveManager or Process Historian.

Does changing the alarm display limit require an OS Server restart?

Modifying Alarm Logging buffer properties requires deactivating and reactivating WinCC Runtime on the OS Server to reinitialize the SQL buffer dimensions.

How can operators locate specific older alarms without increasing the display limit?

Operators can use the Selection button on the Alarm Control toolbar to filter by specific date/time ranges, technological areas, or block tag names.

Technical References

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Related Tags

  • CEMAT
  • Alarm Logging
  • WinCC Alarm Control
  • Short-Term Archive
  • Alarm Sizing
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