Load Imbalance Alarm
The Load Imbalance alarm is raised when:
- The load across instances in the Oracle RAC cluster is significantly unbalanced, and
- The imbalance is proven to be statistically significant, beyond a 95% probability.
Possible causes for this alarm are:
- A mismatch in hardware configuration.
- Poor configuration of client-side TNS files.
- Design or implementation flaws in the Oracle load-balancing algorithms.
- Large batch jobs concentrated on individual nodes in the cluster.
To solve cluster balance problems:
- Rectify any detected hardware configuration problems.
- Improve the load-balancing configuration in client-side TNS files (or elsewhere).
- Balance or schedule batch jobs across nodes.
Note: To select the metric used to represent cluster balance, see Cluster Balance Metric.
Filters on the Load Imbalance alarm
Spotlight can suppress the Load Imbalance alarm in situations where an unbalanced workload does not represent a problem.
- When the load is not significant.
- When required Oracle services cause the imbalance. When a user assigns a non-default Oracle service to a specific instance in the cluster, the extra load may cause some imbalance. Spotlight considers this imbalance significant only when:
- OS monitoring is on.
- At least one instance is showing 100% CPU load (averaged over 5 samples).
- At least one instance is showing less than 80% CPU load (averaged over 5 samples).
