ORA-12560: TNS:protocol adapter error

ORA-12560: TNS:protocol adapter error

You get this error when the listeners port numbers dont match.

You have a port number (1521) specified in tnsnames.ora, There should be a correspondng listener running on the same port on the target database server. If the listener on the target database server is running on a different port, then you get this error.

ORA-12541: TNS:no listener

OK, Almost every body who have worked in Oracle would have seen this error message. This is one of most frustrating and most common error

What does "ORA-12541: TNS:no listener"  mean ?

This means, TNS Listener server is down on the target database server. Check if the listener is up and running.




If your database is running on a windows box, go to services on the database server and check the service is running.

ORA-12545: Connect failed because target host or object does not exist

OK, Almost everbody who has worked in Oracle would have seen this error message. This is one of most frustrating and most common error

What does "ORA-12545: Connect failed because target host or object does not exist"  mean ?


Say from SQLPlus, you are issuing the following command

SQL> Conn scott/tiger@orcldb;

SO, SQLPlus, looks for the entry "orcldb" in your client tnsnames.ora file.

In tnsnames.ora, you will find an entry something similar to this

orcldb=
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = <db_machine_name or ip address>)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = db_name)
    )
  )

so "ORA-12545: Connect failed because target host or object does not exist" means, either your db_machine_name/ip address is incorrect or your machine cannot connect to db_machinge_name/ip_address
for various reasons like network issues etc

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

OK, Almost everbody who has worked in Oracle would have seen this error message. This is one of most frustrating and most common error

What does "ORA-12154: TNS:could not resolve the connect identifier specified"  mean ?


Say from SQLPlus, you are issuing the following command

SQL> Conn scott/tiger@orcldb;

SO, SQLPlus, looks for the entry "orcldb" in your client tnsnames.ora file.

If it cannot find orcldb in tnsnames.ora, then you get ORA-12154: TNS:could not resolve the connect identifier specified

 Fix your tnsnames.ora, and you should be fine.

ORA-12638: Credential retrieval failed

Toad threw this error today, but I was able to connect to the database using SqlPlus.

The problem is coming from your sqlnet.ora

Check if your SQLNET.AUTHENTICATION_SERVICES.  It should be set to NONE instead of NTS

Old entry
SQLNET.AUTHENTICATION_SERVICES= (NTS)

Correct Entry
SQLNET.AUTHENTICATION_SERVICES= (NONE)