Optimizing Alarm Buffer Retention and Archive Query Performance in CEMAT V8.2

When expanding the alarm retention limit beyond 1,000 messages in SIMATIC PCS 7 CEMAT V8.2, system performance and database integrity depend on balancing active RAM message buffers, SQL Server transaction throughput, and long-term archive segmentation. While increasing the Short-Term Archive buffer to 1,500 messages accommodates extended operational logging, expanding active queries without optimization can lead to SQL lock contention and visible screen freezing during plant upsets. Optimizing CEMAT alarm logging requires configuring the WinCC ArchiveManager circular buffer parameters, partitioning message classes into distinct query tabs, and ensuring the SQL database log files are periodically maintained to prevent disk fragmentation.

High-Volume Alarming in Cement and Heavy Process Automation

In heavy industrial applications governed by the CEMAT automation library—such as clinker production lines, vertical roller mills, and conveyor transport networks—an equipment interlock trip frequently triggers an avalanche of secondary alarms (motor overloads, belt misalignments, chute blockages, zero-speed switch trips). During such plant upsets, the standard 1,000-message buffer can fill within minutes.

Engineers frequently seek to expand the retention buffer to 1,500, 3,000, or 5,000 messages. However, naive expansion of buffer sizes in WinCC Alarm Logging without understanding SQL Server circular storage mechanics degrades operator screen responsiveness and increases the risk of archive segment corruption.

SQL Server Circular Buffering and ArchiveManager Architecture

WinCC manages historical messages through the ArchiveManager subsystem, which partitions alarm data into two tiers:

Short-Term Archive (Kurzzeitarchiv): Maintained directly in high-speed RAM and temporary SQL tables (MSRT). It holds active, unacknowledged, and recently cleared alarms. When the buffer reaches its configured limit (e.g., 1,500), the oldest cleared records are purged from the active view according to FIFO (First-In, First-Out) rules.
Long-Term Archive (Langzeitarchiv): Alarms are simultaneously written into persistent, time-sliced Microsoft SQL Server database segments (<ProjectName>_ALG_<Date_Time>.mdf). These segments are archived to disk based on configured time intervals (e.g., 1 week per segment) or maximum file size (e.g., 500 MB).

Balancing performance requires ensuring the Short-Term buffer is large enough for shift review, while SQL circular flushes operate smoothly without blocking real-time PLC message reception.

CEMAT Alarm Logging Performance and Tuning Parameter Matrix

The following table summarizes recommended parameters for high-capacity CEMAT alarm architectures:

Performance ParameterStandard Factory SettingHigh-Capacity Optimized SettingArchitectural ImpactShort-Term Archive Capacity1,000 messages1,500 to 2,000 messagesBalances shift visibility with RAM usageMax Displayed Rows in Control1,000 rows1,500 rows (Filtered)Prevents WinCC client UI thread freezingTime-Sliced Segment Duration1 Month / Segment1 Week / SegmentSpeeds up historical query indexingTotal Archive Size Limit5 GB10 GB to 20 GB (Disk dependent)Prevents hard drive exhaustionSQL Server Recovery ModelSimpleSimpleAutomatically truncates inactive transaction logs

Step-by-Step Optimization Procedure for High-Capacity Alarm Lists

To optimize CEMAT alarm performance while supporting 1,500+ messages:

Configure Circular Buffer in WinCC Alarm Logging:
- Open WinCC Explorer on the OS Server.
- Open Alarm Logging.
- Right-click Archive Configuration -> Message Archive -> Properties.
- Under Size of the short-term archive, set Max. number of messages to 1500.
- Under Time period of all segments, set max size to 10 GB.
- Under Time period of a single segment, set duration to 1 Week (or max size 500 MB).
Implement Filtered Views in CEMAT Alarm Picture:
- Open @C_Alarm.pdl in Graphics Designer.
- Rather than forcing operators to scroll through 1,500 raw rows, configure dedicated toolbar tabs filtering by technological area (e.g., Raw Mill, Kiln Line, Cement Mill).
- In the Alarm Control properties, set Sort Order to descending timestamp (newest alarms at top).
Perform Database Index Maintenance:
- Using SQL Server Management Studio (SSMS), verify that the WINCC database indexes on the message tables are intact and rebuild indexes if query lag exceeds 3 seconds.

Verification

Verify high-capacity alarm performance:
1. In WinCC Runtime, open the CEMAT alarm screen.
2. Verify that the Alarm Control indicates a capacity of 1,500 messages.
3. Perform a screen switch from a complex kiln overview graphic to the alarm screen; verify that complete rendering occurs in less than 2 seconds.
4. Simulate a burst of 50 process alarms; confirm that all alarms are captured without dropping messages or logging MSMQ buffer overflow events in the Windows Event Viewer.

Limitations and Operational Precautions

Avoid Excessive Buffers: Setting short-term archive buffers to extreme numbers (> 10,000) causes severe client hangs during picture changes; use SIMATIC Process Historian for deep historical analysis.
Redundant Server Synchronization: When expanding alarm buffer sizes, the identical configuration must be compiled and downloaded to both Master and Standby OS Servers to maintain redundancy synchronization.
Disk Space Monitoring: High-volume alarm logging accelerates hard drive consumption; ensure server partitions maintain at least 25% free disk space.

Engineer FAQ

Why did my alarm query slow down after increasing the limit to 1500?

Querying 1,500 rows requires SQL Server to scan larger data pages. Splitting segments into smaller time intervals (1 week per segment) restores fast index seek times.

What happens if an alarm flood exceeds 1,500 messages in an hour?

The short-term archive will drop the oldest cleared alarms from the active view, but all 1,500+ messages remain permanently written into the long-term SQL archive segments on disk.

Can I export the 1,500 alarms directly to an Excel file from the CEMAT screen?

Yes. The WinCC Alarm Control toolbar provides an 'Export' button that dumps the currently displayed alarm grid directly into a CSV or text file.

Does CEMAT have its own alarm logging engine separate from WinCC?

No. CEMAT utilizes the native Siemens WinCC Alarm Logging engine and Alarm Control, wrapped in specialized CEMAT graphic faceplates and templates.

Technical References

Related Tags

CEMAT
Alarm Logging
ArchiveManager
Buffer Optimization
WinCC Performance

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Optimizing Alarm Buffer Retention and Archive Query Performance in CEMAT V8.2