Returns the resolved connect string from any configured source (tnsnames, LDAP, Easy Connect) as indicated in the sqlnet.ora names.directory_path parameter
dbms_tns.resolve_tnsname(tns_name IN VARCHAR2) RETURN VARCHAR2;
PRAGMA SUPPLEMENTAL_LOG_DATA(resolve_tnsname, READ_ONLY);
SELECT db_link, dbms_tns.resolve_tnsname(host)
FROM dba_db_links;