[ISS Support Case] Intermittent Trend

Description

The customer reports that trend displays for multiple incubators intermittently stop showing data after a period of operation. Historical data remains present in the MySQL database and can be retrieved manually, indicating that the issue is isolated to the display/trend retrieval process rather than data collection. The problem previously occurred when using the Aveva proprietary trend file format and continues after migrating to MySQL-based storage. When the failure occurs: Trend displays show no data or frozen data. Restarting the Aveva SCADA service or rebooting the PC restores normal operation. Restarting only the MySQL database service does not resolve the issue. Log file analysis shows repeated MySQL errors: Can't create more than max_prepared_stmt_count statements (current value: 16382) This indicates the MySQL server has reached the configured limit for prepared SQL statements. The prepared statement count appears to increase over time without being released, suggesting a resource leak in the trend query handling. Once the limit is reached, all subsequent queries fail until the SCADA service is restarted, which clears the open statements. Impact: Trend displays become non-functional until the SCADA service or PC is restarted. Historical data is unaffected.

• Author: Kevin Modlin
• Published: October 17th, 2025

Details: