SP2-1503: Unable to initialize Oracle call interface

Oracle Error :: SP2-1503

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

Cause

Indicates a library used by SQL*Plus to communicate with the database failed to initialize correctly.
Action
Check that the Oracle environment or registry entries are consistent and correct. If using the SQL*Plus Instant Client make sure the SQL*Plus and Oracle libraries are from the same release. Make sure you have read access to the libraries.

If you are running Vista or Windows 2008 check if the user running the command has Administrative access. If running on Vista/2008/Windows 7, select the .exe and use "Run as Administrator" option .

Unix/Linux
This problem may  related to the $ORA_TZFILE environment variable in Oracle 11GR2 which is no longer needed.

The workaround is to unset the variable and then call sqlplus again

$unset ORA_TZFILE
$sqlplus "/ as sysdba"
sql>

If you use Oracle E-Business Suite 11i or R12 then you have to remove the environment variable ORA_TZFILE also from the database environment file.

At the end of $ORACLE_DATABASE_HOME/SID_host.env there is an entry

######################
# Timezone Specification file
ORA_TZFILE="$ORACLE_HOME/oracore/zoneinfo/timezlrg.dat
export ORA_TZFILE
######################

you must remove it. It shows a file(timezlrg.dat) that no longer exists!

You must also remove the ORA_TZFILE and from $ORACLE_DATABASE_HOME/appsutil/template/ad8idbux.env