2 Identifying and Accessing the Database

Understand how databases are identified, and how clients access them.

• Understanding Database Instances
  A database has at least one instance. An instance is comprised of a memory area called the System Global Area (SGA) and Oracle background processes.
• Understanding Database Services
  An Oracle database is represented to clients as a service. A database can have one or more services associated with it.
• Connecting to a Database Service
  To connect to a database service, clients use a connect descriptor that provides the location of the database and the name of the database service.
• Understanding Service Handlers
  Service handlers act as connection points to an Oracle database. A service handler can be a dispatcher or a dedicated server process, or pooled.
• Understanding Naming Methods
  Oracle Net Services offers several types of naming methods that support localized configuration on each client, or centralized configuration that can be accessed by all clients in the network.
• Enhancing Service Accessibility Using Multiple Listeners
  For some configurations, such as Oracle RAC, multiple listeners on multiple nodes can be configured to handle client connection requests for the same database service.