Apex domains cannot have CNAME records.
Question and response
Question
dig ocs.oraclecloud26.com. NS
Answer
ocs.oraclecloud26.com. 5 NS ns1.p200.dns.me-abudhabi-3.oci.oraclerealm26.com.
ocs.oraclecloud26.com. 5 NS ns2.p200.dns.me-abudhabi-3.oci.oraclerealm26.com.
ocs.oraclecloud26.com. 5 NS ns3.p200.dns.me-abudhabi-3.oci.oraclerealm26.com.
ocs.oraclecloud26.com. 5 NS ns4.p200.dns.me-abudhabi-3.oci.oraclerealm26.com.
ocs.oraclecloud26.com. 5 NS ns5.p200.dns.me-abudhabi-3.oci.oraclerealm26.com.
ocs.oraclecloud26.com. 5 NS ns6.p200.dns.me-abudhabi-3.oci.oraclerealm26.com.
Authority
The response has no authority records.
Additional
ns1.p200.dns.me-abudhabi-3.oci.oraclerealm26.com. 5 A 84.8.20.181
ns2.p200.dns.me-abudhabi-3.oci.oraclerealm26.com. 5 A 84.8.21.184
ns3.p200.dns.me-abudhabi-3.oci.oraclerealm26.com. 5 A 84.8.19.47
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0