SID_XDB service and SID_XPT Service 

In oracle 10g, when you check the listener service, you may notice two particular services registered:
[ccbqa] /orasw/app/oracle/admin/ >lsnrctl status|grep ccbqa
Service "ccbqa" has 1 instance(s).
  Instance "ccbqa", status READY, has 1 handler(s) for this service...
Service "ccbqaXDB" has 1 instance(s).
  Instance "ccbqa", status READY, has 1 handler(s) for this service...
Service "ccbqa_XPT" has 1 instance(s).
  Instance "ccbqa", status READY, has 1 handler(s) for this service...

If you saw XDB service, you database must be configured in shared serve mode:
SQL> show parameter dispa

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
dispatchers                          string      (PROTOCOL=TCP) (SERVICE=ccbqaX
                                                 DB)
max_dispatchers                      integer
SQL> show parameter shared_server

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
max_shared_servers                   integer
shared_server_sessions               integer
shared_servers                       integer     1

Dispatchers and shared_servers can be changed online, to empty and 0, making the server into dedicated mode.

Metalink Note 339940.1 – “How to stop the _XPT service from registering with the listener”. It explains why this service appears.

In version 10.2 of the RDBMS when an instance registers with its listeners it will register a service with the name <sid>_XPT (e.g. v102_XPT) in addition to the normal service names.
This service does not cause a problem and is intended for use within Data Guard environments.

The Note also explains how to resolve the issue.

In the init.ora file for the instance set,
__dg_broker_service_names=''
Please note that this setting begins with two underscore characters. The instance will need to be restarted for this to take effect.

So after taking dispatcher paremeter out from the init.ora, and add __dg_broker_service_names='' into init.ora and restart database, you'll notice the XDB and XPT services are gone:
[ccbqa] /orasw/app/oracle/admin/ >lsnrctl status|grep ccbqa
Service "ccbqa" has 1 instance(s).
  Instance "ccbqa", status READY, has 1 handler(s) for this service...