Apex domains cannot have CNAME records.
Question and response
Question
dig ap-melbourne-1.ocs.oraclecloud.com. NS
Answer
ap-melbourne-1.ocs.oraclecloud.com. 5 NS a6-66.akam.net.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS ns.ap-melbourne-1.dns.oraclerealm1.com.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS a1-143.akam.net.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS ns2.p200.dns.oraclecloud.net.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS a18-65.akam.net.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS ns3.p200.dns.oraclecloud.net.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS ns1.p200.dns.oraclecloud.net.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS a4-67.akam.net.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS a7-64.akam.net.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS ns4.p200.dns.oraclecloud.net.
ap-melbourne-1.ocs.oraclecloud.com. 5 NS a13-64.akam.net.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0