ORA-12560: TNS: protocol adaptor error

you don't need a listener.ora on your client,

what does the listener.ora on your server look like?

Here is the server Listener.ora

LISTENER =
 (ADDRESS_LIST=
(ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=1521))
(ADDRESS=(PROTOCOL=ipc)(KEY=PNPKEY))
 )  

 SID_LIST_LISTENER=
  (SID_LIST=
(SID_DESC=
         (GLOBAL_DBNAME=orcl)
         (SID_NAME=orcl)  
          (ORACLE_HOME=/u01/app/oracle/product/11.1.0/db_1/)
          (PRESPAWN_DESC=(PROTOCOL=tcp)(POOL_SIZE=2)(TIMEOUT=1))
        )
   )

I reread the question and want to confirm, you used sqldeveloper from the server?  or from the client?

If from the server, that doesn't help the diagnosis.
If from the client, then, as suggested above, check for multiple oracle homes and check you used the same connection information for sql developer as you are using for sql plus.

Ive searched, but there is only tnsnames.ora. What I could notice is there is SQL PLUS inside SQL DEVELOPER application and I am able to log-in to the database using that SQL PLUS but not the one from Start-->Programs-->Oracle home-->Application Development-->SQL PLUS.
 
Will this help to resolve the problem?
Thank you in advance.

that seems to support the theory that you have more than one oracle home.

what is your PATH?

where is the sqlplus you are invoking? (check both the command line and what is invoked via sqldeveloper)

If you right click and chose properties for the Start-->Programs-->Oracle home-->Application Development-->SQL PLUS this should tell you where it is running SQL*Plus from, which will identify the directory structure under which SQL*Plus is installed.  Is this a different directory structure to which SQL DEVELOPER is installed?  At the top level of this structure is there a Network\Admin directory and if so is there a tnsnames.ora file in it?  If not, try copying your other tnsnames.ora into this Admin directory.

Can you connect to any databases from SQL*Plus?

When I invoke SQL PLUS from Start-->Programs-->Oracle home-->Application Development-->SQL PLUS, it gives me the TNS error.
Where as if I invoke from Start-->Programs-->Oracle home-->Application Development-->SQL Developer
then Tools-->SQL PLUS, it works.
Where am I standing in this error!
Thank You

Milleniumaire: Both SQL PLUS are launching from same D:/app/product/11.1.0/client_1/....
There only 2 tnsnames.ora in my enitre workstation. One is in D:/app/product/11.1.0/client_1/network/admin and another is in D:/app/product/11.1.0/client_1/network/admin/sample.
Thank You.

To add more, I dont have TNS_Admin entry in my registry. Will this help me to get on to this error?

Are the two copies of SQL*Plus the same i.e. are the menu shortcuts pointing to the same executable?

As you only have one Oracle Home containing one copy of tnsnames.ora, then setting up the TNS_ADMIN environment variable probably won't make any difference.

what is the PATH?

Yes, they are same. Both are in D:/app/product/11.1.0/client_1/BIN.

Hope this is driving strange for you people. I can understand there is a thin line.

It doesn't make sense that two different options on the start menu run exactly the same code, but one gives an error!  Are there any differences between the properties of these two menu items?

how are you connecting in sqlplus (stand alone) vs sql developer?

Are you using TNS in sql developer or "Basic" or "Advanced"  connection type?

:-)

No there are no difference.

I am using Basic in Connection type.

ah!!  basic bypasses tnsnames.ora lookup and goes directly to the server.

is the information in the prompts the same as in your tnsnames.ora?

My tnsnames.ora in client;-

ORCL =
 (DESCRIPTION =
   (ADDRESS_LIST =
     (ADDRESS = (PROTOCOL = TCP)(HOST = OraSrv1)(PORT = 1521))
   )
   (CONNECT_DATA =
     (SERVICE_NAME = orcl)
   )
 )

I used Basic while I connected sqldeveloper. Do I need to change anything on the tnsnames.ora?

what are the "Hostname"  "Port" and "SID/Service name"  fields in sqldeveloper set to for your connection?

Hostname: OraSrv1

Port: 1521

SID/Service Name: orcl

what does your sqlnet.ora look like?

sqldeveloper isn't using your tnsnames.ora because it doesn't need to
but maybe sqlplus isn't either because sqlnet.ora is redirecting to ldap or onames.

what do you get if you "tnsping orcl"  from the command line?

sqlner.ora:-

SQLNET.AUTHENTICATION_SERVICES= (NTS)
NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)

tnsping result:-

D:\>tnsping orcl
TNS Ping Utility for 32-bit Windows: Version 11.1.0.6.0 - Production on 12-JAN-2
009 21:10:21
Copyright (c) 1997, 2007, Oracle.  All rights reserved.
Used parameter files:
D:\app\product\11.1.0\client_1\network\admin\sqlnet.ora

Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)
(HOST = OraSrv1)(PORT = 1521))) (CONNECT_DATA = (SID = orcl) (SERVER = DEDICATED
)))
OK (100 msec)

when you connect with sqlplus you should get something like the snippet below
what are your typing at the prompt that generates the error?

Can you cut and paste your screeen text?

SQL*Plus: Release 11.1.0.6.0 - Production on Mon Jan 12 10:43:16 2009
 
Copyright (c) 1982, 2007, Oracle.  All rights reserved.
 
Enter user-name:

                                              

1:
2:
3:
4:
5:

yah sure,

Wow... It worked :-)

Thanks a lot.

The answer was perfect.