Database Reference
In-Depth Information
App Server
SCAN
Listener
Clients
Database
Listener
Figure 11-2.
SCAN and database listeners
Ip aDDreSS
an ip address is a four-part number with each part represented by a number between 0 and 255. part of that ip
address represents the network the computer exists on, whereas the remainder identifies the specific host on
that network. the four-part number is selected based on the size of the network in the organization. network
sizes are classified into three classes based on the size. Class a has a number between 0 and 127, Class B has a
number between 128 and 191, and Class C has a number between 192 and 223. an example of an ip address is
192.168.200.60
.
Database Listeners
The database listener, also called Oracle Net Listener, is responsible for making routing requests received from clients
to the right databases by mapping the service request handle from the client connection to the services that are
registered with the listener.
When a database instance starts, the instance establishes a communication path with the listener using a new
background process in Oracle 12c “listener registration process” (LREG). The LREG process provides the listener with
the instance name, database service name, and the type and addresses of service handlers. This information is used
by the listener to route client requests to the respective database instances.
Load Balancing
One primary feature of a clustered environment is to distribute workload across the various nodes/instances in the
cluster. To achieve this distribution, it would be advantageous to place new connections on systems that have a higher
number of resources in the cluster.
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