Right now the <systemUsage> configuration in conf/activemq.xml is commented. If commented then the default systemUsage defined in BrokerService.getSystemUsage() takes effect.
I don't think many users are aware of the default systemUsage settings. I know of some users that thought there are no systemUsage restrictions enforced when this configuration is commented.
So rather than commenting out <systemUsage> in our default configuration, why not enabling it with the same settings as the default systemUsage (which anyway takes effect when the <systemUsage> config is commented)?
IMHO it will make it more clear to users what limits are currently enforced.
We should also leave a comment in the <systemUsage> config that disabling this config makes the broker use the default settings.