Memory errors/exceptions

In some circumstances, whilst using the CAST Engineering Dashboard/Discovery Portal, you may receive Low Memory/Recovered Memory/Out of Memory errors or exceptions, for example:

[WARNING]: [MEM] Low Memory: 24052448
[WARNING]: [MEM] Recovered Memory: 18348800

These errors and exceptions are displayed by the Java Virtual Machine and they indicate that the Java Garbage Collector is in operation. As a result, you may see a slow down in performance. You can ignore these errors, however, if they persist, it is possible to modify the JVM memory configuration settings to resolve the problem.

The procedure for modifying the JVM memory settings is dependent on how you have installed Tomcat - either as a service or standalone (launched via the command line) and is fully documented in Appendix - web application server configuration.

Performance in an Oracle environment following a snapshot generation

When using the CAST Engineering Dashboard/Discovery Portal in an Oracle environment, you may find that for a period of time immediately following the generation of a snapshot, performance is adversely affected. After this period of time, performance returns to expected levels.

The period of time when performance is affected is determined by the interval set on your Oracle server to automatically flush monitoring statistics - by default this is set to 15 minutes. When this flush occurs, new statistics that have been generated automatically by CAST on completion of a snapshot generation (via a call to the package DBMS_STATS) are made effective and performance is improved via the use of the up-to-date monitoring statistics.

If you would like to manually update the monitoring statistics to avoid the period of degraded performance, please refer to the Oracle Performance Tuning Tips on calling DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO().