By default the JMX diagnostic subsystem is always enabled, but external access is password-protected and requires opening the diagnostic port in your firewall as described in Exposing Diagnostics Through Jaspersoft's JMX Agent. If you wish to disable all external access, see Disabling Remote Connections to the JMX Agent.
Internally, the diagnostics subsystem is passive and has no performance impact until it is accessed in a report through the diagnostic data source. However, if you wish to disable real-time diagnostics entirely, rename or remove the following files:
In that case, the diagnostic data source, the sample report, and the sample Topic described in Using the Diagnostic Data in Reports will not function either. They can be deleted from the repository.