OCI: APEX does not show up in DBA_REGISTRY

We had a case where moving a customer from OCIC to OCI with apex caused issues. We could not find dba_registry on OCI.

Follow this,
https://cloud.oracle.com/iaas/whitepapers/oracle_apex_on_oci_database.pdf

[gsdsiConnect] ORA-28040, ORA-28040: No matching authentication protocol

We had upgraded the OID database from 12.1 to 12.2 , post that when starting OID we got the below error.

[2019-07-29T04:24:20.342724-06:00] [OID] [NOTIFICATION:16] [] [OIDMON] [host: aXXXXXXX] [pid: 40240] [tid: 0] Guardian: [gsdsiConnect] ORA-28040, ORA-28040: No matching authentication protocol
[2019-07-29T04:24:20.343169-06:00] [OID] [NOTIFICATION:16] [] [OIDMON] [host: aXXXXXXX] [pid: 40240] [tid: 0] Guardian: [oidmon]: Unable to connect to database,will retry again after 10 sec

So, this is known error when we move from 11g to 12c database. Then we just have to make sec_case_sensitive_logon   parameter to false and it used to work. But in this case, the parameter didnot help. So, i created a sqlnet.ora updated below,

SQLNET.ALLOWED_LOGON_VERSION=11

This fixed the issue and OID was started.