oracle database running but not listening

Question

I installed a 11.2020 11g EE Oracle Database

SQL> select * from v$version
  2  ;

BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE    11.2.0.2.0      Production
TNS for Linux: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production

Initially, everything is good and it listens on port 1521 until I shut down the server.

After restarting, I start the database by running startup

SQL> startup
ORACLE instance started.

Total System Global Area 1603411968 bytes
Fixed Size                  2226912 bytes
Variable Size            1342178592 bytes
Database Buffers          251658240 bytes
Redo Buffers                7348224 bytes
Database mounted.
Database opened.

However, the database does not listen and I am unable to connect to the instance.

I can find it in processes but not under the netstat.

# ps -ef | grep pmon
ocsgapp  12005     1  0 08:42 ?        00:00:00 ora_pmon_orcl
root     12615 12596  0 09:05 pts/1    00:00:00 grep pmon


# netstat -an | grep 1521
#

I haven't changed anything since installation and the content of listener.ora is as the following

# cat /home/ocsgapp/app/ocsgapp/product/11.2.0/dbhome_1/network/admin/listener.ora
# listener.ora Network Configuration File: /home/ocsgapp/app/ocsgapp/product/11.2.0/dbhome_1/network/admin/listener.ora
# Generated by Oracle configuration tools.

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = freeze.dev.unico.com.au)(PORT = 1521))
    )
  )

ADR_BASE_LISTENER = /home/ocsgapp/app/ocsgapp

I tried to reinstall the whole database and it was listening on 1521 after installation. However, it failed to recover after another shutdown. Does anyone have idea why the db is running but fail to listen on a 1521?

Solution

The database does not listen for incoming connection requests from clients. That is the job of a separate process, the listener. It appears that you haven't set your listener to start up when the server restarts. If that's the case, you'd need to start the listener

./lsnrctl start

If you're not sure whether the listener is running

./lsnrctl status