Entity
Name DATABASE INSTANCE SERVICE
Definition
A Database Instance Service is defined as a logical representation of a database, which is the way a database is presented to clients. A database can be presented as multiple services and a service can be implemented as multiple database instances. The service name is a string that is the global database name, that is, a name comprising the database name and domain name, entered during installation or database creation.
http://docs.oracle.com/cd/B19306_01/network.102/b14212/glossary.htm

Attribute
Name Definition Datatype Required Is PK Is FK
Database Instance Service Identifier A Database Instance Service Identifier is the unique value assigned to represent the Service Name running on a particular database instance. INTEGER Yes Yes No
Database Instance Service Name A Database Instance Service Name is the word or words by which a particular database instance is known by. VARCHAR(100) No No No
Database Instance Identifier A Database Instance Identifier is a unique value assigned to represent a particular instance of a database. INTEGER Yes No Yes