As a general rule, dynamic registration is a better option, but there are circumstances when you will resort to static registration. Dynamic registration was introduced with release 8i, but if you have older databases that your listener must connect users to, you will have to register them statically. Also, some applications may require static registration: typically, management tools. To register an instance statically, take the Static Database Registration link within Database Control, and enter the name of the service, the name of the instance, and the location of the ORACLE_HOME directory for that instance, as shown in Figure 12-5. In a simple, single-instance, environment the service name and the instance name will often be the same, but if you are in any doubt about this, log in to your instance using SQL*Plus and check the values of the parameters INSTANCE_NAME and SERVICE_NAMES by querying the V$PARAMETER.
If SERVICE_NAMES was not set in your parameter file, it will have defaulted to the INSTANCE_NAME suffixed with the DB_DOMAIN. The default for DB_DOMAIN is NULL.   _{Your Comment}