# System Properties

Properties files let you configure the global behavior of Horizon. Configuration can also affect the Java virtual machine under which Horizon runs. You must restart Horizon for changes to take effect. Access the configuration files in ${OPENNMS_HOME}/etc. The priority for Java system properties is as follows: 1. Those set via the Java command line i.e., in opennms.conf via ADDITIONAL_MANAGER_OPTIONS 2. opennms.properties.d/*.properties 3. opennms.properties 4. libraries.properties 5. rrd-configuration.properties 6. bootstrap.properties Property files in opennms.properties.d/ are sorted alphabetically.  To avoid conflicts with customized configurations, you can add all custom properties to one or more files in${OPENNMS_HOME}/etc/opennms.properties.d/. We recommend not to modify default OpenNMS properties. Create dedicated files with your customized properties in opennms.properties.d/.