SP2-1503: Unable to initialize Oracle call interface in Oracle 11g

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

Done intial checking :

>> user oracle was in the correct database admin group (/etc/group)
>> No tnsnames issues as TNS_ADMIN variable is poiting to correct directories and all files( tnsnames.ora, sqlnet.ora, listener.ora) in it have valid entries.
>> $PATH variable was pointing to correct $ORACLE_HOME/bin

On checking the environment variable closely, it was found that one of the variable ORA_TZFILE was pointing to non-existent file.

echo $ORA_TZFILE

/u01/oracle/dev/db/tech_st/11.2.0/oracore/zoneinfo/timezlrg.dat

ls -ltr /u01/oracle/dev/db/tech_st/11.2.0/oracore/zoneinfo/timezlrg.dat

ls: /u01/oracle/dev/db/tech_st/11.2.0/oracore/zoneinfo/timezlrg.dat: No such file or directory

This file timezlrg.dat was not present at the location, though there were other files with names like
timezone_<N>.dat.

–

—
-rw-r–r– 1 oradev dba 507957 Aug 18 2011 timezlrg_2.dat
-rw-r–r– 1 oradev dba 493675 Aug 18 2011 timezlrg_1.dat
-rw-r–r– 1 oradev dba 791430 Aug 18 2011 timezlrg_14.dat
-rw-r–r– 1 oradev dba 782475 Aug 18 2011 timezlrg_13.dat
-rw-r–r– 1 oradev dba 785621 Aug 18 2011 timezlrg_12.dat
-rw-r–r– 1 oradev dba 787272 Aug 18 2011 timezlrg_11.dat
-rw-r–r– 1 oradev dba 792894 Aug 18 2011 timezlrg_10.dat
—
–
Unsetting this variable solved our issue.

$ unset ORA_TZFILE

$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Tue Oct 16 11:45:08 2012

Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 – 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL>
We can also set and use the desired timezone file and if we do not set it then by default it will use maximum value of n.

export ORA_TZFILE=$ORACLE_HOME/oracore/zoneinfo/timezlrg_<N>.dat