ORA-12154: TNS:could not resolve the connect identifier specified Error and Solution

by on May 1, 2008 · 11 comments· LAST UPDATED May 1, 2008

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Q. My Oracle XE installation was working fine, but today I'm getting an error - which read as follows under Ubuntu Linux :

ORA-12154: TNS:could not resolve the connect identifier specified

How do I fix this problem without reinstalling Oracle?

A. Try following solutions:

Make sure DNS / host name resolution working fine

$ host oracle-server-ip
$ host oracle-server-hostname

Make sure /etc/resolv.conf and /etc/hosts and /etc/host.conf configured properly.

Make sure tnsnames.ora is configured properly:

Type the following command to login as oracle / dba user:
$ su - oracle
$ cd /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin/
$ vi tnsnames.ora

Make sure hostname / IP is correctly defined and resolving perfectly:

# tnsnames.ora Network Configuration File:
XE =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = vivek-desktop)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = XE)
    )
  )
EXTPROC_CONNECTION_DATA =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
    )
    (CONNECT_DATA =
      (SID = PLSExtProc)
      (PRESENTATION = RO)
    )
  )

Make sure the host, port and service name specified are correct in listener.ora and above file:
$ cd /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin/
$ vi listener.ora

My sample working file:

# listener.ora Network Configuration File:
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = /usr/lib/oracle/xe/app/oracle/product/10.2.0/server)
      (PROGRAM = extproc)
    )
  )
LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC_FOR_XE))
      (ADDRESS = (PROTOCOL = TCP)(HOST = vivek-desktop)(PORT = 1521))
    )
  )
DEFAULT_SERVICE_LISTENER = (XE)

Make sure firewall is not blocking TCP ports:
$ sudo iptables -L -n
If everything else failed try to trace problem by running strace:
$ su - oracle
$ strace -o /tmp/debug.sqlplus sqlplus user/password

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{ 11 comments… read them below or add one }

1 venu R May 19, 2008 at 8:37 am

Dear sir,

Thank you for send the every time latest infomation on linux based and also do me some help to me.
How do i install Oracle10g on RedHat Enterprises Linux 5 kindly send me the same with step by step.

Thanks & Regards,
Venu R,
IT Dept,
Avantha Technologies Ltd
Secunderabad.

Reply

2 Ashwin Patel January 30, 2011 at 1:03 am

Send me an email, i’ll send you complete step by step installation of Oracle 10g on Linux RHEL3, 4 , 5 , 6. Also its the same procedure to install 11g.

Ashwin Patel

Reply

3 Raju ponthapillli January 9, 2009 at 4:41 am

this solution very useful to biggners to change listener.ora and tnsnames.ora file
to configure system

Reply

4 manoj kulkarni March 7, 2011 at 10:13 am

i have configure SDU and TDU configuration in tnsnames.ora and listener.ora
file to increase the network performance , but now iam getting error code 12154 while connecting through sqlplus…………. my all syntax for the above files are correct there is no any spell mistake.

please giude me.

manoj kulkarni
microstop infotech.
india.

Reply

5 zbhknight October 1, 2011 at 3:29 am

So strange, it always reports an error which says TNS-12533 illegal address parameters
I have get the debugging file, but I don’t know how to analyse it.

Reply

6 Suresh.Rapaka January 18, 2012 at 5:20 am

Hi,

Even i did all modifications, getting same error…

Can you help me more in this issue ?

Thanks in advance

Suresh

Reply

7 nbs March 12, 2012 at 6:47 am

i also have this problem. how to solve this problem.

Reply

8 preetha April 11, 2012 at 3:42 pm

$ su – oracle
$ cd /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin/
$ vi tnsnames.ora
where to type these commands and how to check?

Reply

9 preetha April 11, 2012 at 3:46 pm

$ host oracle-server-ip
$ host oracle-server-hostname
where to type these command and how to check?

Reply

10 Javed May 14, 2012 at 7:34 am

Clean some space on disk.

Reply

11 ahmed October 30, 2013 at 10:14 am

thank you from the answer

Reply

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