For DAUs to be usable on the service-layer, the feature must be enabled both system-wide and on the content-store(s). For the feature to be usable through ReST (outside the JVM) the rest-api configuration must also be enabled.
The system.directAccessUrl.enabled property is the main switch for this feature. If this is set to false, then all DAUs are disabled.
The next configuration that controls specific DAUs is the one for the content store. The connector.s3.directAccessUrl.enabled property controls whether DAUs are enabled for that specific store.
Whether a client can request a DAU by using a ReST endpoint is controlled by the restApi.directAccessUrl.enabled property. If the ReST endpoint is disabled, but the feature is enabled system-wide and on the content-store, then the DAUs will only be usable by Java clients (i.e. only service-level requests will be possible).