With the release of APM 10.0, a new feature called Differential Analysis was introduced. This capability makes use of a new database called variance.db located in the <EM Home>\data directory.
Are there any ways to reduce or limit the size of the variance.db file?
Any version of APM 10.0 or higher
Currently there are no pruning or maintenance operations run on variance.db. This database will increase in size until the number of metrics baselined by the Differential Analysis feature reaches the value specified by the Enterprise Manager property: introscope.enterprisemanager.baseline.max.metrics.baselined.
This property is listed in the <EM Home>\config\IntroscopeEnterpriseManager.properties file and has a default value of 20,000:
# Total number of metrics allowed to be baselined per collector.
So how can I reduce the size of variance.db?
To reduce the size of variance.db, it is recommended to
1-Shut down the Enterprise Manager
2-Delete the current variance.db file from the <EM Home>\data directory.
3-Lower the value of introscope.enterprisemanager.baseline.max.metrics.baselined in
the <EM Home>\config\IntroscopeEnterpriseManager.properties file.
4-Restart the EM
What value should I set introscope.enterprisemanager.baseline.max.metrics.baselined to?
This answer will varies depending on the disk space available to the EM. You can estimate this value by checking the current number of metrics being baselined by the EM and adjust accordingly. The number of metrics currently being baselines is available as a supportability metric in the Workstation Investigator in the metric path: Super Domain | Custom Metric Host (Virtual) | Custom Metric Process (Virtual) | Custom Metric Agent (Virtual) (Super Domain) | <Enterprise Manager Instance> | Baseline Engine | Total Metrics Baselined (count).
Also be aware that the <EM Home>\config\IntroscopeEnterpriseManager.properties file contains the following property:
# How long an inactive metric remains in the baselining cache before it is evicted
This property does not have any effect on the size of variance.db, but rather controls the rate at which variance data expires from the in-memory cache. This value is measured in ms with a default value of 300 seconds.
More information about the Differential Analysis feature can be found here:
Release: CEMUGD00200-10.1-Introscope to CA Application-Performance Management-Upgrade Mai