SQL> select tenuser from tbluser@db_link_orclbalv.anhnt;
select tenuser from tbluser@db_link_orclbalv.anhnt

create public database link db_link_orclbalv.anhnt connect to user identified by pass using 'orclbalv';

12514, 00000, "TNS:listener does not currently know of service requested in connect descriptor"
// *Cause:  The listener received a request to establish a connection to a
// database or other service. The connect descriptor received by the listener
// specified a service name for a service (usually a database service)
// that either has not yet dynamically registered with the listener or has
// not been statically configured for the listener.  This may be a temporary
// condition such as after the listener has started, but before the database
// instance has registered with the listener.
// *Action: 
//  - Wait a moment and try to connect a second time.
//  - Check which services are currently known by the listener by executing:
//    lsnrctl services <listener name>
//  - Check that the SERVICE_NAME parameter in the connect descriptor of the
//    net service name used specifies a service known by the listener.
//  - If an easy connect naming connect identifier was used, check that
//    the service name specified is a service known by the listener.
//  - Check for an event in the listener.log file.