Based on Oracle documentation on DNS Service Provider for the JNDI, Context.PROVIDER_URL ("java.naming.provider.url") may be used to specify a set of DNS servers to use. Currently, our DefaultDnsResolver always sets this environment property to "dns:" when creating InitialDirContext. This means that if a user specifies a URI with the dns scheme as a value of this property to override the set of DNS servers, the driver ignores that. Maybe we should only set Context.PROVIDER_URL if its value is not already a URI with the dns scheme.