Oracle Error :: SP2-1503 Unable to initialize Oracle call interface SP2-0152: ORACLE may not be functioning properly

Oracle Error :: SP2-1503 Unable to initialize Oracle call interface

Cause
Indicates a library used by SQL*Plus to communicate with the database failed to initialize correctly.

Action
1)  Check that the Oracle environment variable are set properly .
2) If using the SQL*Plus Instant Client make sure the SQL*Plus and Oracle libraries are from the same release
3) Make sure you have read access to the libraries.

In my case there are both 10g and 11g are installed on same server . and 11g is default home .now i want to connect with oracle 10g home on the server

I have export the  ORACLE_BASE, ORACLE_HOME, ORACLE_SID

$export ORACLE_BASE=/home/oracle/apps
$ export ORACLE_HOME=$ORACLE_BASE/product/db_1/10.2.0
$ export ORACLE_SID=DB01

and run sqlplus and got below error

$ sqlplus / as sysdba
SP2-1503: Unable to initialize Oracle call interface
SP2-0152: ORACLE may not be functioning properly

Then i have export the path  with above environment variables which i set earlier

$ export PATH=/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin
$ PATH=$PATH:$HOME/bin:$ORACLE_HOME/bin:/bin:/usr/lib64/:$ORACLE_HOME/OPatch

and it sucessfully connected


$ sqlplus / as sysdba
Connected to:
Oracle Database 10g Release 10.2.0.4.0 - 64bit Production