ORA-12547: TNS:lost contact

When I tried to login into oracle I have received below error
sapec4:ec4adm 61> sqlplus /nolog

SQL*Plus: Release 11.2.0.2.0 Production on Thu Sep 29 14:00:17 2011

Copyright (c) 1982, 2010, Oracle. All rights reserved.

SQL> connect / as sysdba
ERROR:
ORA-12547: TNS:lost contact

Here is the simple solution for that

Solution1:-
1.Check “oracle:dba” should have ownership on $ORACLE_HOME/bin/sqlplus
$chown oracle:dba $ORACLE_HOME/bin/sqlplus
2.$ORACLE_HOME/bin/sqlplus should have 6751 permission
$chmod 6751 $ORACLE_HOME/bin/sqlplus

If you still have the problems try solution 2.

Solution2:-
You may receive this error if oracle binaries are not linked correctly, stop databases and relink the binaries.

$ ORACLE_HOME/bin/ relink all

If you find below errors in listener.log then problem related to limit of PROCESSES value.

TNS-12500: TNS:listener failed to start a dedicated server process
TNS-12547: TNS:lost contact
TNS-12560: TNS:protocol adapter error
TNS-00517: Lost contact

Solution:- Increase the PROCESSES parameter in the init.ora to a higher value
SQL> Alter system set processes= “”

After fixing TNS issue you may see below error

ORA-27140: attach to post/wait facility failed

Solution:-
$ cd $ORACLE_HOME/bin
$ chmod 6751 oracle

Regards,
Satishbabu Gunukula
http://www.oracleracexpert.com