OCM 12c Preparation - Configure the network environment to allow connections to multiple databases

> This topic is pretty the same thing as we had in OCM 11g exam. But now as we have a container database scenario, we open more options. <

You can run multiple listeners in the same server. Thus, it's possible to:

• Have 1 listener pointing to multiple databases services.
• Have multiple listeners pointing to a single service.
• Have multiple listeners pointing to multiple services.
• Having a listener pointing only to a single PDB.

By default, when you start a listener without a listener.ora, it will listen on 2 addresses:

(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=hostname)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))

Also, by default, the database will register itself to the TCP listener running on localhost and port 1521. The PMON is the process responsible for it and does that every 60 seconds. You can force the register running: "alter system register".

So, if you have a lot of databases in the same environment, all of them will be automatically registered to the default listener as soon as it is running and the local_listener is with the default value as well.

If you want to set up the static listener pointing to all the DBs, you must need to know how to define static entries. This is very important and needed for a lot of DB tasks, like rman duplication, data guard FSFO, etc.

For this topic, what I recommend studying is:

• Using netca / netmgr to create listener.ora and tnsnames.ora.
• Creating listener.ora and tnsnames.ora manually.
• Creating services for connection to a determined PDB.
• How to set up static listener in listener.ora.
• The ways local_listener parameter can be defined (even adding an entry in tnsnames.ora and referring to it)

Path to Documentation:

Database Administration -> Net Services Administrator's Guide -> 9 Configuring and Administering Oracle Net Listener

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