Unable to initialize Oracle call interface

Sometimes ASA an db upgrade, the DB instance may encounter below issue while you try to connect,

-bash-3.00$ sqlplus / as sysdba
SP2-1503: Unable to initialize Oracle call interface
SP2-0152: ORACLE may not be functioning properly
-bash-3.00$ 

The probably issue is that after DB upgrade, the timezone file has gone. Hence you have to reset ORA_TZFILE.

Solution:

unset ORA_TZFILE

Reason:

-bash-3.00$ echo $ORA_TZFILE

/u01/oracle/mydb/11.2.0/oracore/zoneinfo/timezlrg.dat

-bash-3.00$ ls /u01/oracle/mydb/11.2.0/oracore/zoneinfo/timezlrg.dat

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

-bash-3.00$ unset ORA_TZFILE

-bash-3.00$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Fri Jun 14 07:05:51 2013

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 – Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

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