ORA-12641: Authentication service failed to initialize

Error Description:
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Whenever I tried to logon to my database it failed me with error ORA-12641.
-bash-3.00$ sqlplus shaik/shaik@moon/shaik.india.com

SQL*Plus: Release 10.2.0.2.0 - Production on Tue Jun 24 05:55:52 2008

Copyright (c) 1982, 2005, Oracle. All Rights Reserved.

ERROR:
ORA-12641: Authentication service failed to initialize

Cause of The problem:
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In the $ORACLE_HOME/network/admin/sqlnet.ora file SQLNET.AUTHENTICATION_SERVICES is set to ALL and Secure Network Services has not been used.

Whenever Secure Network Services is not being used, that is you try to logon to database using SQL*Net from database host computer using above command, then it explicitly disallow applications from initiating SQL*Net connect requests with authentication services. So to allow connection through SQL*Net it is needed to disable authentication services while still allowing normal SQL*Net connections.

Soltion of The Problem:
---------------------------------
Issuing the above command from another computer rather than host will not produce the error because in that case secure network services will be used.

To disable SQL*Net authentication services while still allowing normal SQL*Net connections you can set in $ORACLE_HOME/network/admin/sqlnet.ora the following line,

SQLNET.AUTHENTICATION_SERVICES =(NONE)

Now try to connect and it will be ok.
-bash-3.00$ sqlplus shaik/shaik@moon/shaik.india.com
SQL*Plus: Release 10.2.0.1.0 - Production on Tue Jun 24 06:10:32 2008

Copyright (c) 1982, 2005, Oracle. All rights reserved.


Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options