Oracle Data Provider for .NET opens a port to listen for database notifications when the following features are used:
HA Events
Load Balancing
Database change notification
All three of these features share the same port, which can be configured centrally by setting the db notifications port in an application or web configuration file.
If the configuration file does not exist or the db notification port is not specified, ODP.NET uses a valid, random port number. The configuration file may also request for a random port by specifying a db notification port value of -1. To specify a particular port, for example, 1200, an application or web configuration file can be used as shown below.
<configuration>
<oracle.dataaccess.client>
<settings>
<add name="db notification port" value="1200"/>
</settings>
</oracle.dataaccess.client>
</configuration>
The port number should be unique for each process running on a computer. Thus, the port number should be set uniquely for each application either programmatically or through an application config file. Note that if the specified port number is already in use, ODP.NET does not provide any errors. For details on configuring ODP.NET, see "ODP.NET Configuration".
When the process using ODP.NET starts, the application reads the db notification port number and listens on that port. Once the port is opened, the port number cannot be changed during the lifetime of the process.