oakcli delete database: ORA-12154: TNS:could not resolve the connect identifier specified

When i try to delete the database using oakcli command:

oakcli delete database -db mydb

... the error "ORA-12514: TNS:listener does not currently know of service requested in connect " is generated.

It is not the known bug with db_names and also occurs with newly generated databases.

I get a connection error when the oakcli script uses these connect string:

    $DB_HOME/bin/sqlplus -L sys/password@:1521/mydb as sysdba

but there is no scan listener name like in the correct connection:

    $DB_HOME/bin/sqlplus -L sys/password@scanname:1521/mydb as sysdba

What's the reason?

PS:

# srvctl config scan_listener -i 1