The Listener （concept)【每日一译】--20121205

When an instance starts, a listener process establishes a communication pathway to

Oracle. When a user process makes a connection request, the listener determines

whether it should use a shared server dispatcher process or a dedicated server process
and establishes an appropriate connection.
The listener also establishes a communication pathway between databases. When
multiple databases or instances run on one computer, as in Real Application Clusters,
service names enable instances to register automatically with other listeners on the
same computer. A service name can identify multiple instances, and an instance can
belong to multiple services. Clients connecting to a service do not have to specify
which instance they require.

当一个实例启动时，一个监听进程创建了一个联系通道到ORACLE。当一个用户进程发送了

一个连接请求，监听决定是否将使用共享服务收发进程或者是专有服务进程并且创建一个合适

的连接。

监听也可以创建联系通道在多个数据库之间。当多个数据库或者是实例运行在一台电脑时，像RAC,

服务名允许实例动态注册使用同一台电脑上的其它监听。一个服务名可以识别多个实例，并且一个

实例可以属于多个服务。客户端连接到服务器不需要指定需要哪个实例。

Service Information Registration
Dynamic service registration reduces the administrative overhead for multiple
databases or instances. Information about the services to which the listener forwards
client requests is registered with the listener. Service information can be dynamically
registered with the listener through a feature called service registration or statically
configured in the listener.ora file.

服务注册

动态服务注册减少了管理多个库或者实例的消耗。对于关于监听转发客户需求服务信息

是通过监听注册。服务信息可以被动态注册使用监听通过一个叫做服务注册功能或者是通过

静态在LISTENER.ORA文件的配置。

Service registration relies on the PMON process—an instance background process—to
register instance information with a listener, as well as the current state and load of the
instance and shared server dispatchers. The registered information enables the listener
to forward client connection requests to the appropriate service handler. Service
registration does not require configuration in the listener.ora file.

服务注册依赖于PMON进程-一个实例的后台进程-通过一个监听注册实例的信息，以及当前

实例状态和负载以及共享服务调度。注册信息允许监听转发客户的连接请求到相应用服务处理。

服务注册不要求配置LISTENER.ORA文件

The initialization parameter SERVICE_NAMES identifies which database services an
instance belongs to. On startup, each instance registers with the listeners of other
instances belonging to the same services. During database operations, the instances of
each service pass information about CPU use and current connection counts to all of
the listeners in the same services. This enables dynamic load balancing and connection
failover.

初始化参数SERVICE_NAMES识别哪个实例属于哪个数据库服务。在库启动时，每个实例

通过其它实例的监听注册在同一个服务器上。在数据操作时，每个服务器的实例通过同一个服务器

传递关于CPU使用和当前连接用户数使用监听。它允许动态载平衡和连接转移。