How to Resolve TNS-12541: TNS:no listener

TNS-12541

Let’s see how we reproduce TNS-12541.

C:\Users\ed>tnsping compdb

TNS Ping Utility for 64-bit Windows: Version 12.1.0.1.0 - Production on 22-JUL-2014 19:20:06

Copyright (c) 1997, 2013, Oracle.  All rights reserved.

Used parameter files:
C:\oracle\app\client\ed\product\12.1.0\client_1\network\admin\sqlnet.ora


Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = primary01)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = compdb)))
TNS-12541: TNS:no listener

Cause

The connection cannot find the listener, it could be not started or at another port, e.g. 1522.

Solution

Check the status and port of LISTENER on server side and start it if necessary.

[oracle@primary01 ~]$ lsnrctl status

LSNRCTL for Linux: Version 12.1.0.1.0 - Production on 22-JUL-2014 19:22:34

Copyright (c) 1991, 2013, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
TNS-12541: TNS:no listener
 TNS-12560: TNS:protocol adapter error
  TNS-00511: No listener
   Linux Error: 2: No such file or directory
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=primary01)(PORT=1521)))
TNS-12541: TNS:no listener
 TNS-12560: TNS:protocol adapter error
  TNS-00511: No listener
   Linux Error: 111: Connection refused

As you can see, the database port is 1521 without questions. But the listener is not started. So let’s start it up.

[oracle@primary01 ~]$ lsnrctl start

LSNRCTL for Linux: Version 12.1.0.1.0 - Production on 22-JUL-2014 19:23:59

Copyright (c) 1991, 2013, Oracle.  All rights reserved.

Starting /u01/app/oracle/product/12.1.0/dbhome_1/bin/tnslsnr: please wait...

TNSLSNR for Linux: Version 12.1.0.1.0 - Production
System parameter file is /u01/app/oracle/product/12.1.0/dbhome_1/network/admin/listener.ora
Log messages written to /u01/app/oracle/diag/tnslsnr/primary01/listener/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=primary01)(PORT=1521)))

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 12.1.0.1.0 - Production
Start Date                22-JUL-2014 19:23:59
Uptime                    0 days 0 hr. 0 min. 2 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /u01/app/oracle/product/12.1.0/dbhome_1/network/admin/listener.ora
Listener Log File         /u01/app/oracle/diag/tnslsnr/primary01/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=primary01)(PORT=1521)))
The listener supports no services
The command completed successfully

For more testing skills, you may check Oracle 18c Net Services Administrator’s Guide: 15 Testing Connections.