Hi If it helps you think about dynamic service registration as being all about the server advertising its services. tnsnames is all about clients being told where to look for a particular service, and what to ask for when they get there. On 27 Jan 2011 21:43, "sundar mahadevan" <sundarmahadevan82@xxxxxxxxx> wrote: Hi All, Sorry about this basic question. I can understand how dynamic registration works but does dynamic listener service registration completely eliminate the use of tnsnames.ora or do i keep the tnsnames.ora and change the sid to service_name. Thanks in advance.