RAC/Exadata -- Scan listener registration problem, EBS 11i , autoconfig TNS-12514

You may encounter a scan listener registration problem after enabling autoconfig on your EBS database tier. Altough , everything including remote_listener, local_listener parameters as well as network related oracle conf file such as tnsnames.ora,sqlnet.ora and listener.ora may seem perfect, the dynamic registration from EBS database to the scan listener(pointed by the remote_listener parameter) can be problematic.
This problem is encountered in an Exadata X6 environment, on which we hosted an EBS 11i environment with a 12C Oracle database.

The problem is directly related with autoconfig, as autoconfig in some cases can not handle RAC specific configuration perfectly well.
In this case, autoconfig creates a tns entry named as the scan_name:port  and actually creates it wrongly by putting the vips as for the host entry. Like below;

SCAN_NAME:SCAN_PORT =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = exa1vip)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = exa2vip)(PORT = 1521))

The result is ORA-12514 / TNS-12514 when trying to connect to scan name and port .

The solution is; removing the scan_name:scan_port tns entry from the tnsnames.ora , as there should not be any tns entry for registering the scan listener, no need.

After removing the tns entry, it is better to refill the remote_listener and make the pmon to register the database to all available listeners using alter system register; as shown in the following example;

sqlplus / as sysdba
alter system set remote_listener='' scope=both sid='*';
alter system set remote_listener='exa-rac:1521' scope=both sid='*';
alter system register;

Also, it is important to keep in mind that this solution should be reimplemented everytime the autoconfig is run.

An alternative maybe, modifying the autoconfig templates or codes to fix this issue, but it won't be supported and actually I dont have time for this , these days :)